Ecology Questions

1) Distinguish between populations, communities, and ecosystems.

a) Population: A population refers to all the individuals of a single species
that live in a specific area at a given time. These individuals can
interact, interbreed, and share a common gene pool. For example, a
population of monarch butterflies in a specific forest.
b) Community: A community consists of all the different populations of
species that live and interact within a specific area. This includes
multiple species that may be producers, consumers, or decomposers,
and the interactions such as predation, competition, or mutualism. For
example, a forest community includes trees, birds, insects, mammals,
and fungi.
c) Ecosystem: An ecosystem encompasses both the biological community
and the abiotic (non-living) environment in which they live and
interact. It includes the flow of energy and cycling of nutrients between
organisms and their environment, such as sunlight, water, air, and
minerals. For example, a pond ecosystem involves fish, aquatic plants,
water chemistry, sunlight, and soil.
2) Demonstrate how the world “guild” is used in ecology.
a) In ecology, a guild refers to a group of species that exploit the same
class of environmental resources in a similar way, regardless of their
taxonomic relationships. Members of a guild share similar ecological
niches, meaning they perform similar roles in the ecosystem, but they
do not necessarily belong to the same species or even family.
b) Insect-eating birds: Various species of birds, such as woodpeckers,
flycatchers, and swallows, may all belong to the same guild if they feed
primarily on insects. Despite being different species with varied
behaviors, they exploit a common resource (insects) in similar ways
(catching or foraging).
3) How does a guild relate to a population and a community?
a) A guild consists of multiple species that exploit similar resources in the
same way, whereas a population is all individuals of a single species.
Within a community (all species in an area), guilds represent functional
groupings of species based on resource use, cutting across different
populations. A guild highlights shared ecological roles within a broader
community.
4) Many terms are used in a variety of ways. How is the term
community used in ecology?
 a) In ecology, a community refers to all the different populations of
species that live and interact within a particular area. It includes the
plants, animals, fungi, and microorganisms that coexist and interact
through processes like predation, competition, and symbiosis. A
community encompasses all the biotic (living) components of an
ecosystem.

5)
a) How do you know this is a community?
b) What drives the formation of this zonation?
c) Where do you think there would be the greatest species diversity in
this figure?
6) Understand the role keystone species plan in a community and
how they affect species diversity.
a) A keystone species plays a crucial role in maintaining the structure and
stability of a community. Despite their relatively low abundance, they
have a disproportionate impact on the ecosystem by influencing the
populations of other species. By controlling prey populations, providing
essential resources, or modifying the habitat, keystone species help
maintain species diversity. If removed, the community can become
unbalanced, often leading to reduced biodiversity and changes in
ecosystem function.
b) Example: Sea otters are keystone species in kelp forest ecosystems. By
preying on sea urchins, they prevent the overgrazing of kelp,
preserving the habitat for a wide range of species.
7) What does it mean that keystone species shape a community?
a) When a keystone species shapes a community, it means that the
species has a critical role in determining the structure and dynamics of
the community. Its presence regulates populations of other species,
maintains ecological balance, and supports the overall health of the
 ecosystem. By influencing interactions such as predation, competition,
and habitat modification, a keystone species helps maintain species
diversity and ecosystem stability. Without it, the community can
collapse or change drastically, often leading to reduced biodiversity.
8) What is a major predator?
a) A major predator is an organism at or near the top of the food chain
that hunts, kills, and consumes other animals (prey) for food. These
predators play a crucial role in regulating prey populations, maintaining
ecological balance, and shaping community structure. By controlling
the abundance of herbivores or smaller predators, major predators can
influence species diversity and prevent overgrazing or overpopulation
of certain species.
b) Example: Wolves in a forest ecosystem are major predators, helping to
regulate populations of deer and other herbivores.
9) Is every predator a keystone species?
a) No, not every predator is a keystone species. While predators can
influence prey populations, a keystone species has a disproportionate
impact on the overall community and ecosystem structure. Many
predators affect their prey, but only some have critical roles that shape
the diversity and functioning of the ecosystem. Keystone species
uniquely maintain balance, and their removal often leads to significant
changes in the ecosystem, while the loss of other predators may not
have the same profound effect.
10) Identify possible keystone and index species in different
communities.
a) Keystone Species:
i) Sea Otters (kelp forests): Control sea urchin populations, preventing
overgrazing of kelp and maintaining habitat diversity.
ii) Wolves (grasslands and forests): Regulate herbivore populations,
which helps maintain vegetation health and biodiversity.
iii) Beavers (wetlands): Create dams that transform landscapes,
promoting diverse aquatic habitats and influencing water flow.
b) Index Species:
i) Trout (freshwater ecosystems): Sensitive to pollution and habitat
changes, indicating water quality.
ii) Lichens (terrestrial ecosystems): Sensitive to air quality; their
presence or absence indicates levels of air pollution.
iii) Coral (marine ecosystems): Indicators of reef health; their decline
signals changes in water temperature and quality.
11) Distinguish between species richness and equitability.
 a) Species richness refers to the total number of different species present
in a particular area or community, indicating biodiversity. In contrast,
equitability (or species evenness) measures how evenly individuals are
distributed among the different species in that area. High equitability
means that species are represented in similar numbers, while low
equitability indicates that one or a few species dominate. Together,
species richness and equitability provide a more comprehensive
understanding of biodiversity in an ecosystem.
12) Diversity and richness are often used interchangeably.
a) While diversity and richness are related concepts in ecology, they are
not interchangeable. Species richness specifically refers to the count of
different species in a given area. In contrast, diversity often
encompasses both species richness and equitability, reflecting not just
the number of species but also how evenly individuals are distributed
among those species. Therefore, diversity provides a more
comprehensive measure of ecosystem health and complexity than
richness alone.
13) Present the competitive exclusion principle. What is this
principle based upon?
a) The competitive exclusion principle states that two species competing
for the same limited resource cannot coexist indefinitely in the same
niche; one species will outcompete and exclude the other. This
principle is based on the idea that when two species have identical
requirements for resources (such as food, habitat, or light), the species
that is more efficient in exploiting those resources will thrive, while the
other will be driven to extinction or forced to adapt to a different niche.
Essentially, it highlights the importance of resource competition in
shaping community structure and biodiversity.
14) What does it mean by community structure?
a) Community structure refers to the composition and arrangement of
different species within a community, including their abundance,
distribution, and relationships with one another. It encompasses factors
such as species diversity, species richness, trophic levels, and the
physical organization of species in the habitat. Community structure
influences ecosystem functioning, resilience, and stability, as well as
how species interact with each other and their environment.
Understanding community structure is essential for studying ecological
dynamics and biodiversity.
15) “Two species so similar that they compete for the same
limiting resources cannot coexist in the same area.” Explain.
Really? Are there exceptions? Is this always true?
a) The statement reflects the competitive exclusion principle, which
suggests that two species that are too similar in their ecological
requirements (niche) cannot coexist in the same area if they compete
for the same limited resources. One species will typically outcompete
the other, leading to its extinction or local elimination.
i) Resource Partitioning: Species may coexist by utilizing different
resources or exploiting the same resource in different ways or at
different times (e.g., birds feeding at different heights in a tree).
ii) Niche Differentiation: Species may evolve adaptations that allow
them to exploit slightly different niches, reducing direct competition.
iii) Environmental Variability: Fluctuations in resource availability can
allow similar species to coexist temporarily.
iv) While the competitive exclusion principle provides a general
guideline for understanding species interactions, it is not an
absolute rule. Coexistence is possible through resource partitioning,
niche differentiation, and other ecological mechanisms.
16) What is your niche?
a) In ecology, a niche refers to the specific role or function an organism
plays within its ecosystem, encompassing its habitat, resource use,
and interactions with other species. This includes factors such as what
it eats, where it lives, how it reproduces, and how it responds to
environmental conditions.
b) For example, a niche could be described as a bird species that
primarily feeds on insects in a forest canopy, nesting in tree hollows,
and competing with other insectivorous birds. Each species has a
unique niche that helps to reduce competition and allows for
coexistence within a community.
17) Often niche is used to refer to an organisms habitat but, as
you can see, its really include much more than that.
a) Yes, that's correct. While a niche is often mistakenly equated with an
organism's habitat, it encompasses much more. A niche includes not
only the physical environment where an organism lives (habitat) but
also its role in the ecosystem, such as its feeding behavior,
reproductive strategies, interactions with other species (predation,
competition, symbiosis), and its response to abiotic factors (like
temperature and moisture). Essentially, a niche represents the full set
of environmental conditions and resources an organism requires to
 survive and reproduce, reflecting its unique place within the
ecosystem.
18) Be able to present what is included in an organism’s niche.
a) An organism’s niche includes several components:
i) Habitat: The physical environment where the organism lives.
ii) Resource Use: The type of food and other resources the organism
consumes (e.g., plants, animals, nutrients).
iii) Feeding Behavior: How the organism obtains food (e.g., herbivore,
carnivore, omnivore).
iv) Reproductive Strategies: Methods of reproduction, such as mating
habits and breeding seasons.
v) Interactions: Relationships with other organisms, including
competition, predation, mutualism, and parasitism.
vi) Physiological Tolerances: The range of environmental conditions
(temperature, moisture, pH) that the organism can withstand.
19) The key here is “significant differences”. What make a
difference significant?
a) In ecology, significant differences refer to variations in ecological data
or patterns that are meaningful and not due to random chance. These
differences can impact the structure, dynamics, and functioning of
ecosystems. Factors that make a difference significant include:
i) Magnitude: The size of the difference matters; larger differences are
more likely to be ecologically meaningful.
ii) Statistical Significance: Results from statistical tests (e.g., t-tests,
ANOVA) that indicate whether observed differences are likely due to
chance or reflect true patterns.
iii) Ecological Relevance: The difference should have implications for
species interactions, community structure, or ecosystem processes
(e.g., nutrient cycling, energy flow).
iv) Contextual Factors: The ecological context, such as species roles,
environmental conditions, and temporal factors, can influence the
significance of differences.
b) In summary, a significant difference in ecology is one that has
substantial implications for understanding and managing ecological
systems, beyond mere statistical variations.
20) What is localized extinction?
a) Localized extinction, also known as extirpation, occurs when a species
ceases to exist in a specific area or habitat but continues to survive in
other locations. This type of extinction can happen due to various
factors, including habitat destruction, pollution, overexploitation, or
 competition from invasive species. Localized extinction can disrupt
local ecosystems and may have cascading effects on other species
that depend on the extinct species for food, pollination, or other
ecological functions.
21) Present the concept of resource partitioning as it relates to the
competitive exclusion principle.
a) Resource partitioning is a concept that explains how similar species
can coexist in the same habitat by utilizing different resources or
exploiting the same resources in various ways. This adaptation reduces
direct competition, which is central to the competitive exclusion
principle, which states that two species competing for the same limited
resources cannot coexist indefinitely.
b) By partitioning resources—such as feeding at different times, foraging
in different areas, or using different types of food—species can
minimize overlap and competition. For example, two bird species might
feed on insects in the same tree but occupy different heights, allowing
them to coexist despite competing for the same resource. Resource
partitioning thus serves as a mechanism that allows species to avoid
competitive exclusion and maintain biodiversity in ecosystems.
22) Do you see the relationship between resource availability,
competition, resource partitioning, the competitive exclusion
principle, and species diversity? Explain species diversity using
these concepts.
a) Yes, there is a significant relationship among resource availability,
competition, resource partitioning, the competitive exclusion principle,
and species diversity.
i) Resource Availability: The quantity and type of resources (food,
habitat, etc.) in an ecosystem determine how many species can
survive and thrive.
ii) Competition: When resources are limited, species compete for those
resources. Intense competition can lead to the competitive
exclusion principle, where one species outcompetes another for the
same resources.
iii) Resource Partitioning: To reduce competition and avoid exclusion,
species may adapt by partitioning resources. This allows similar
species to coexist by utilizing different aspects of the available
resources (e.g., feeding at different times or on different food
types).
iv) Competitive Exclusion Principle: This principle highlights that two
species cannot occupy the same niche if they compete for identical
 resources. It leads to the idea that coexistence is possible only
through resource partitioning.
v) Species Diversity: As species partition resources and reduce
competition, it promotes coexistence and increases species
diversity within an ecosystem. High species diversity contributes to
ecosystem stability and resilience, allowing it to better withstand
environmental changes.
b) In summary, resource availability shapes competition, which can lead
to either exclusion or diversity through mechanisms like resource
partitioning, ultimately influencing the overall species diversity in an
ecosystem.
23) Present the varied impact plants can have on animal
communities.
a) Plants can have varied impacts on animal communities in several
ways:
i) Habitat Structure: Plants provide physical structures that offer
shelter, nesting sites, and foraging areas for animals. Dense
vegetation can support a diverse array of species, while open areas
may support fewer.
ii) Food Source: Plants are primary producers and serve as a crucial
food source for herbivores. The availability and type of vegetation
directly influence herbivore populations and, subsequently, the
predators that rely on them.
iii) Microclimate Regulation: Plants can modify microclimates by
providing shade, reducing wind, and retaining moisture. This can
create suitable conditions for certain animal species while making it
inhospitable for others.
iv) Pollination and Seed Dispersal: Many plants rely on animals for
pollination and seed dispersal, forming mutualistic relationships.
These interactions can affect plant reproductive success and the
distribution of both plants and animals.
v) Chemical Interactions: Some plants produce allelochemicals that
can inhibit the growth or reproduction of certain animal species.
Conversely, others may produce compounds that attract animals for
mutualistic benefits.
vi) Invasive Species: Non-native plant species can disrupt local
ecosystems, outcompeting native plants and altering habitat
structure, which can negatively affect the animal communities that
depend on native flora.
 b) In summary, plants play a critical role in shaping animal communities
through habitat provision, food availability, climate regulation, and
interactions that influence population dynamics and biodiversity.
24) Could plant help regulate population size?
a) Yes, plants can help regulate population size in animal communities
through several mechanisms:
i) Food Availability: The abundance and nutritional quality of plant
resources directly influence herbivore populations. If food is
plentiful, herbivore populations may increase; conversely, a decline
in plant availability can lead to a decrease in herbivore populations.
ii) Habitat Structure: Plants provide shelter and breeding sites for
animals. Changes in plant density and diversity can affect the
survival and reproduction rates of animal populations, influencing
their overall size.
iii) Competition: The presence of certain plant species can affect the
distribution and abundance of herbivores and other animals through
competition for resources. This can limit the population size of
competing species.
iv) Chemical Defense: Some plants produce secondary metabolites that
can deter herbivores or reduce their reproductive success. This can
lead to decreased herbivore populations, thereby regulating their
size.
v) Predator Attraction: Plants can attract predators by providing
habitats or food sources, indirectly regulating the populations of
herbivores by increasing predation pressure.
b) In summary, plants play a crucial role in regulating population sizes of
animal communities through their influence on food availability,
habitat structure, competition, chemical interactions, and predator
dynamics.
25) Present the varied ways that plants defend themselves against
being eaten to extinction.
a) Plants defend themselves against herbivory through various strategies:
i) Physical Defenses: Structures like thorns, tough leaves, and
trichomes deter herbivores.
ii) Chemical Defenses: Toxic compounds and secondary metabolites
make plants unpalatable or harmful to herbivores.
iii) Mimicry and Camouflage: Some plants resemble inedible objects,
reducing their recognition as food.
iv) Mutualistic Relationships: Partnerships with ants or pollinators can
provide protection against herbivores.
 v) Phenological Changes: Timing growth and reproduction to avoid
peak herbivore activity helps minimize damage.
vi) Regrowth Abilities: Rapid regrowth after damage allows plants to
recover and persist.
vii) Growth Forms: Adopting low-growing or slow-growing forms can
reduce herbivory risks.
b) These strategies collectively enhance plant survival and prevent
extinction in the face of herbivore pressures.
26) Present the varied defenses prey have against predators.
a) Prey species have evolved various defenses to protect themselves
from predators:
i) Camouflage: Blending into the environment helps prey avoid
detection. This can include color matching or disruptive patterns.
ii) Mimicry: Some prey species mimic the appearance of toxic or
unpalatable species (Batesian mimicry) or resemble harmless
species to confuse predators (Müllerian mimicry).
iii) Chemical Defenses: Many prey produce toxic or unpalatable
chemicals that deter predators. Examples include poison in frogs
and unpleasant tastes in certain insects.
iv) Physical Defenses: Structures such as shells, spines, or thick skin
provide protection from physical attacks.
v) Behavioral Defenses: Prey may use evasive actions, such as fleeing,
freezing, or engaging in distraction displays (e.g., playing dead) to
escape predators.
vi) Group Living: Social behaviors, such as living in groups (herds,
schools, flocks), can reduce individual predation risk through
vigilance and dilution effects.
vii) Warning Coloration: Bright colors can signal that a species is
toxic or unpalatable, warning predators to avoid them.
viii) Habitat Selection: Prey may choose habitats that provide cover
or refuge from predators, such as dense vegetation or burrows.
b) These varied defenses help prey species survive in the face of
predation and contribute to the dynamics of predator-prey interactions.
27) Present the different types of mimicry they are used by plants
and animals.
a) Mimicry is a strategy used by plants and animals to avoid predation or
enhance survival. The main types of mimicry include:
i) Batesian Mimicry: A harmless species mimics the appearance of a
harmful or unpalatable species to deter predators. For example,
some non-venomous butterflies resemble toxic species.
 ii) Müllerian Mimicry: Two or more unpalatable or harmful species
evolve similar warning colors or patterns, reinforcing the avoidance
behavior in predators. An example is the shared coloration of
various toxic wasps and bees.
iii) Aggressive Mimicry: A predator or parasite mimics a harmless or
beneficial organism to deceive prey or hosts. For instance, some
anglerfish use a lure that resembles small fish or invertebrates to
attract prey.
iv) Automimicry (Intraspecific Mimicry): An organism mimics its own
body parts to confuse predators or rivals. For example, some snakes
have tail coloration that resembles their heads, misleading
predators.
v) Flower Mimicry: Some plants mimic the appearance of flowers that
attract pollinators, often resembling other species that provide
rewards. For example, certain orchids imitate the shape and scent
of female insects to attract male pollinators.
b) These types of mimicry enhance survival by either deterring predators
or facilitating successful predation and reproduction.
28) Why don’t predators drive their prey to extinction?
a) Predators do not typically drive their prey to extinction due to several
ecological mechanisms:
i) Population Dynamics: Predator and prey populations often exhibit
dynamic interactions characterized by fluctuations. As predator
populations increase, prey populations may decline, leading to
reduced predator numbers when food becomes scarce, allowing
prey populations to recover.
ii) Adaptation: Prey species evolve various defensive adaptations (e.g.,
camouflage, speed, chemical defenses) that improve their chances
of survival against predators, which can maintain a balance in the
predator-prey relationship.
iii) Resource Availability: Prey species often have high reproductive
rates, allowing them to recover quickly from predation pressures.
This resilience can prevent their extinction, even when faced with
high predation.
iv) Habitat Heterogeneity: Diverse habitats provide refuges and
resources that allow prey to survive and escape predation. This
spatial variation can reduce the overall impact of predation on prey
populations.
 v) Behavioral Strategies: Prey species may develop behaviors such as
grouping together, vigilance, or nocturnal activity to minimize
predation risks, further ensuring their survival.
vi) Mutual Interdependence: The predator-prey relationship is part of a
broader ecosystem where various species interact. Other factors,
such as food availability and environmental conditions, also
influence population dynamics, allowing prey to persist despite
predation.
b) Together, these mechanisms create a balance that prevents predators
from driving their prey to extinction, contributing to the stability of
ecosystems.
29) How does this work with herbivores?
a) The dynamics between herbivores and their plant prey follow similar
principles as those between predators and prey, which help prevent
herbivores from driving plants to extinction:
i) Population Dynamics: Herbivore populations can fluctuate in
response to the availability of plant resources. When herbivore
numbers increase and overconsume plants, this can lead to a
decline in herbivore populations due to food scarcity, allowing plant
populations to recover.
ii) Plant Defenses: Plants have evolved various defenses against
herbivory, including physical (thorns, tough leaves) and chemical
(toxins, deterrent compounds) adaptations that reduce herbivore
feeding and increase plant survival.
iii) High Reproductive Rates: Many plant species can reproduce quickly
and produce large numbers of seeds. This reproductive strategy
allows them to recover from herbivory and maintain populations
despite being consumed.
iv) Habitat Diversity: Varied habitats provide different plant species and
microenvironments that can support plant survival. Some plants
may thrive in areas less accessible to herbivores.
v) Herbivore Behavior: Herbivores may exhibit behaviors to minimize
their impact on plant populations, such as foraging selectively or
migrating to areas with abundant food.
vi) Ecological Interactions: The herbivore-plant relationship exists
within a larger ecosystem context, where other factors (such as soil
nutrients, competition among plants, and climate) influence
population dynamics and resilience.
 b) These mechanisms work together to maintain a balance between
herbivores and plants, preventing the overconsumption of plants and
ensuring that both groups can coexist within their ecosystems.
30) One BIG question to keep in mind for the first exam is what
controls species diversity. Review all of the different factors that
aid in rich species diversity.
a) Species diversity is controlled by several interconnected factors that
contribute to the richness and variety of species within ecosystems:
i) Habitat Heterogeneity: Diverse physical environments (e.g.,
different soil types, topography, and microclimates) create varied
niches, allowing more species to coexist.
ii) Resource Availability: The abundance and diversity of resources
(food, water, shelter) support a wide range of species. Greater
resource variety can lead to higher species richness.
iii) Climate: Stable and favorable climatic conditions (temperature,
precipitation) promote higher species diversity. For example,
tropical regions generally have greater biodiversity due to
consistent warmth and moisture.
iv) Disturbance Patterns: Moderate disturbances (e.g., fires, storms)
can enhance diversity by creating new habitats and opportunities
for different species. However, excessive disturbance can reduce
diversity.
v) Species Interactions: The dynamics of predator-prey relationships,
competition, mutualism, and facilitation can influence community
structure and support diverse populations.
vi) Evolutionary History: The historical context of an area, including
past climatic shifts and geological events, shapes current
biodiversity patterns. Areas with complex histories often have
higher species richness.
vii) Isolation and Connectivity: Geographic isolation (e.g., islands)
can lead to unique species evolution, while habitat connectivity
allows for gene flow and species movement, enhancing diversity.
viii) Human Impacts: Human activities, such as habitat destruction,
pollution, and climate change, can negatively affect species
diversity. Conversely, conservation efforts can protect and restore
biodiversity.
b) By considering these factors, we gain a comprehensive understanding
of the dynamics that control species diversity within ecosystems.
31) Predator Offense, I have a hundred different way to eat your
butt. Explain.
 a) The phrase "I have a hundred different ways to eat your butt" playfully
highlights the diverse strategies predators use to capture and consume
their prey. In ecology, predator offense refers to the various
adaptations and tactics predators employ to increase their hunting
success. Here are some key strategies:
i) Ambush Predation: Some predators remain still and hidden, waiting
for unsuspecting prey to come close before launching a quick attack
(e.g., crocodiles, certain snakes).
ii) Chase and Pursuit: Many predators rely on speed and stamina to
chase down prey. This is common in carnivores like cheetahs, which
can sprint quickly over short distances.
iii) Pack Hunting: Social predators, such as wolves or lions, work
together in groups to hunt larger prey, increasing their chances of a
successful kill.
iv) Use of Tools: Some predators, like certain birds and primates, use
tools to access prey. For example, woodpecker finches use sticks to
extract insects from tree bark.
v) Deception and Mimicry: Predators may use camouflage or mimicry
to deceive prey, making it easier to approach undetected.
vi) Chemical Cues: Some predators, like certain spiders or insects, can
produce chemical signals to attract prey or enhance their hunting
efficiency.
vii) Subduing Techniques: Once prey is captured, predators may
employ various methods to subdue it, such as constriction (snakes)
or venom (some spiders and snakes).
viii) Adaptation to Prey Type: Different predators have specific
adaptations that enhance their ability to hunt particular prey types,
such as sharp teeth for tearing flesh or specialized beaks for
cracking shells.
b) These varied predatory strategies contribute to the complex dynamics
of ecosystems, illustrating the intricate relationships between
predators and their prey.
32) Explain how soil composition, precipitation, topography, and
elevation can create ecological zonation.
a) Soil composition, precipitation, topography, and elevation significantly
influence ecological zonation by affecting the types of vegetation and
animal communities present in different areas:
i) Soil Composition: Nutrient content and texture determine which
plant species can thrive, influencing plant diversity and community
structure.
 ii) Precipitation: The amount and distribution of rainfall shape
vegetation types, with wet regions supporting forests and arid areas
leading to deserts or grasslands.
iii) Topography: Landscape features create microclimates and
variations in sunlight exposure, resulting in different plant
communities on slopes and valleys.
iv) Elevation: Changes in elevation lead to temperature gradients,
causing shifts in ecosystems from lower elevation forests to alpine
meadows and tundra.
b) Together, these factors interact to create distinct ecological zones,
each with unique communities adapted to their specific environments.
33) These are all example of disturbances that can cause
succession to occur.
a) Disturbances that can cause ecological succession include:
i) Natural Disturbances:
(1)Wildfires: Clear existing vegetation, allowing new species to
colonize.
(2)Flooding: Alters landscapes, creating new habitats for
colonization.
(3)Hurricanes and Storms: Uproot trees and change ecosystems,
prompting succession.
ii) Human-Induced Disturbances:
(1)Deforestation: Removes vegetation, creating opportunities for
new species.
(2)Urban Development: Disrupts ecosystems, leading to new plant
and animal communities.
(3)Pollution: Degrades habitats, shifting community composition.
iii) Biological Disturbances:
(1)Invasive Species: Outcompete local species, altering community
dynamics.
(2)Disease: Reduces certain species' populations, allowing others to
thrive.
(3)These disturbances initiate primary or secondary succession,
leading to the gradual recovery and development of new
community structures over time.
34)
a) When was diversity the lowest?
b) When was diversity the highest?
c) When was the population most equitable?
d) When was the population least equitable?
35) Characterize pioneer species. How do these characteristics aid
in them being pioneers?
a) Pioneer species are the first organisms to colonize previously disturbed
or barren environments, playing a crucial role in ecological succession.
They possess several key characteristics that enable them to thrive in
harsh conditions:
i) High Reproductive Rates: Pioneer species often have rapid growth
and high reproductive output, allowing them to quickly establish
populations in new areas.
ii) Resilience: They can tolerate extreme conditions, such as poor soil
quality, limited moisture, and high levels of sunlight. This resilience
helps them survive in environments where other species might
struggle.
iii) Adaptability: Pioneer species are often highly adaptable to changing
conditions, which allows them to exploit available resources
effectively.
iv) Soil Improvement: Many pioneer species, such as lichens and
certain grasses, can improve soil quality by breaking down rock,
adding organic matter, and fixing nitrogen. This creates a more
favorable environment for subsequent species.
v) Facilitation: By altering the environment (e.g., providing shade,
reducing erosion), pioneer species can create conditions that
 support the establishment of more complex communities, paving
the way for later successional species.
36) Describe and distinguish between primary and secondary
succession.
a) Primary and secondary succession are processes through which
ecosystems develop over time, but they occur under different
conditions. Primary succession takes place in lifeless or barren areas
where no soil exists, such as after a volcanic eruption or glacial retreat.
It begins with pioneer species like lichens and mosses that colonize
bare rock, initiating soil formation and gradually leading to a mature
ecosystem. This process is typically slow, often taking hundreds to
thousands of years. In contrast, secondary succession occurs in areas
that have been disturbed but still have existing soil and some
organisms, such as after a forest fire or flood. It generally progresses
more rapidly due to the presence of soil and seed banks, allowing for
quicker re-establishment of plant communities. Secondary succession
can often take a few decades to a couple of hundred years to reach a
mature state. Overall, primary succession starts from bare rock with no
soil, while secondary succession occurs in areas with existing soil,
leading to different rates and dynamics of ecosystem recovery.
37) Explain how habitat disturbances can affect species diversity.
a) Habitat disturbances can significantly impact species diversity in
various ways, both positively and negatively:
i) Reduction in Diversity: Severe disturbances, such as deforestation,
pollution, or extreme weather events, can lead to the loss of species
by destroying habitats and altering ecosystem dynamics. This
reduction can result in decreased species richness and even
localized extinctions, particularly affecting specialized or vulnerable
species.
ii) Creation of Opportunities: Disturbances can also create new
habitats and opportunities for colonization. For example, after a fire,
the removal of dominant vegetation allows light and resources to
reach the ground, enabling pioneer species to establish and
potentially increasing overall diversity over time.
iii) Shift in Community Composition: Disturbances can alter the balance
of species interactions, such as predation and competition. This shift
may favor certain species over others, leading to changes in
community structure and diversity.
iv) Facilitation of Succession: Disturbances often initiate ecological
succession, which can enhance species diversity as new
 communities develop and stabilize. This process allows for the
introduction of new species and the gradual return of a more
diverse ecosystem.
v) Impact on Resilience: Frequent or intense disturbances may reduce
an ecosystem's resilience, making it more challenging for diverse
species to recover and adapt. Conversely, moderate disturbances
can promote diversity by creating a dynamic environment that
supports various species.
38) Explain the shifting mosaic model of succession.
a) The shifting mosaic model of succession describes ecosystems as
dynamic and patchy landscapes where different areas exist at various
stages of succession simultaneously. Unlike traditional linear models,
this approach emphasizes spatial heterogeneity, where disturbances
(natural or human-induced) create a mosaic of habitats undergoing
change. As certain patches recover from disturbances, others may be
in early successional stages, leading to a mix of habitats that support
greater species diversity. This model highlights the continuous and
non-linear nature of ecological change, underscoring the importance of
understanding both spatial and temporal dynamics in ecosystem
management and conservation.
39) Give an example of cyclic replacement in a community.
a) An example of cyclic replacement in a community can be observed in
temperate grasslands, particularly through the interactions between
fire and plant communities. In these ecosystems, periodic fires act as a
natural disturbance that can reset plant succession.
i) Initial State: After a fire, the landscape is often dominated by
pioneer species, such as annual grasses and forbs, that quickly
colonize the area.
ii) Succession: Over time, these pioneer species create conditions that
support the growth of perennial grasses and eventually shrubs. As
the plant community matures, it increases biodiversity and alters
soil composition, moisture retention, and nutrient availability.
iii) Cyclic Replacement: After a certain period, if a fire occurs again, it
removes the established vegetation, allowing the cycle to restart.
The process continues, with each fire leading to the regeneration of
early successional species and the eventual re-establishment of a
diverse community.
40) Is there such a thing as a climax community? Present and
defend your response.
 a) The concept of a climax community refers to a stable ecological
community thought to reach a point of equilibrium in succession.
However, modern ecological understanding suggests that this idea is
overly simplistic, as ecosystems are inherently dynamic and subject to
continuous change. Factors such as climate variations, natural
disturbances, and human activities can alter species composition and
community structure, leading to multiple stable states rather than a
single climax community. Disturbances can reset succession, resulting
in new community structures rather than returning to a predetermined
endpoint. Therefore, it is more accurate to view climax communities as
part of an ongoing continuum of ecological change influenced by
various biotic and abiotic factors.
41) Give an example of the process of facilitation during
succession.
a) An example of facilitation during succession is the role of nitrogen-
fixing plants in primary succession, such as alder trees in a newly
formed landscape like a volcanic field or glacial moraine. In these
environments, the soil is typically poor in nutrients.
i) Pioneer Species: Alder trees, which are pioneer species, establish
themselves in these nutrient-poor soils. They have a symbiotic
relationship with nitrogen-fixing bacteria in their root nodules,
allowing them to convert atmospheric nitrogen into a form usable
by plants.
ii) Facilitation: Over time, the alders enrich the soil by adding nitrogen,
which improves the soil's fertility. This process facilitates the
establishment of other plant species that require more nutrient-rich
soil, such as grasses, shrubs, and eventually larger trees.
42) “The ecological impact of the tree species may not be realized
until the trees are relatively large.” What does that mean?
a) This statement means that the ecological impact of a tree species
often becomes more significant as the trees grow larger and mature.
When trees are young, their influence on the environment might be
minimal, but as they grow, they can:
i) Alter Microclimates: Larger trees create shade, regulate
temperature, and reduce wind speeds, which can affect the growth
of understory plants and the overall community structure.
ii) Modify Resource Availability: Mature trees have extensive root
systems that influence soil composition, moisture retention, and
nutrient cycling, benefiting or competing with other species.
 iii) Provide Habitat: Large trees offer habitat for various animals,
including birds, insects, and mammals, playing a key role in the
biodiversity of the ecosystem.
iv) Carbon Storage: Bigger trees also sequester more carbon,
contributing to climate regulation.
b) Thus, the full ecological role of tree species often isn't fully expressed
until they reach a certain size and can exert a greater influence on
their surroundings.
43) Autogenic changes can facilitate colonization by other species
or they may also inhibit them.
a) Autogenic changes are environmental modifications caused by the
organisms themselves as they grow and interact with their
surroundings. These changes can either facilitate or inhibit colonization
by other species.
i) Facilitation: Some species modify the environment in ways that
make it more suitable for other species. For example, plants can
enrich the soil with nutrients, improve water retention, or provide
shade, creating better conditions for new species to colonize.
ii) Inhibition: On the other hand, certain autogenic changes can make
the environment less hospitable for other species. For instance, as
trees grow, they may cast dense shade that prevents light from
reaching the forest floor, limiting the growth of shade-intolerant
species. Similarly, some plants release chemicals into the soil
(allelopathy) that inhibit the growth of other plants.
b) Thus, autogenic changes can either promote or hinder the colonization
of new species, depending on how they alter the environmental
conditions.
44) Light captured by leaves can begin to shade the ground which
will cause changes in the ground cover community
a) As leaves of growing plants and trees capture light, they create shade,
reducing the amount of sunlight that reaches the ground. This shading
effect causes significant changes in the ground cover community:
i) Reduction in Sunlight: Shade-tolerant plants may thrive, while
species that require direct sunlight may struggle to grow or
disappear entirely.
ii) Altered Species Composition: The shift in light availability can lead
to a change in the types of plants present, favoring those that are
adapted to lower light levels, such as ferns and mosses.
 iii) Microclimate Changes: Shading also influences temperature and
moisture levels, often leading to cooler and more humid conditions
at ground level, further affecting which species can survive.
b) Overall, as trees and other vegetation grow and cast shade, the ground
cover community shifts, favoring plants that are adapted to lower light
conditions.
45) Production of detritus can pave the way for detritivores.
a) The production of detritus—dead organic material such as fallen
leaves, dead plants, and animal remains—creates a food source for
detritivores, organisms that feed on decomposing organic matter.
b) As detritus accumulates, it attracts detritivores like earthworms, fungi,
and bacteria, which break down the material into smaller particles and
release nutrients back into the soil. This process not only recycles
nutrients, making them available to plants, but also supports a diverse
community of decomposers, further contributing to ecosystem health
and nutrient cycling. In this way, detritus paves the way for
detritivores, playing a crucial role in maintaining ecosystem function.
46) Are there climax communities?
a) The traditional concept of climax communities, where ecosystems
reach a stable, unchanging state after succession, is now considered
overly simplistic. Ecosystems are dynamic and subject to continuous
change due to factors such as climate shifts, natural disturbances, and
human activities. Instead of a single, permanent climax state,
ecosystems often experience multiple stable states or ongoing cycles
of disturbance and recovery. Therefore, while some ecosystems may
reach temporary stability, the idea of a permanent, unchanging climax
community is no longer widely accepted in
47) Explain the concept of cyclic replacement. Are climax
communities real?
a) Cyclic replacement refers to a process in which certain ecosystems
experience recurring disturbances (like fire, storms, or herbivory) that
periodically reset the successional stages within the community. This
leads to a cycle where different stages of succession are continuously
replaced by earlier ones without reaching a permanent, stable state.
b) As for climax communities, the traditional concept of a single, stable
endpoint after succession is now viewed as oversimplified. Modern
ecology recognizes that ecosystems are dynamic, constantly
influenced by disturbances and environmental changes. While some
ecosystems may reach temporary stability, they are often subject to
ongoing shifts, so the idea of a permanent, unchanging climax
 community is not widely accepted today. Instead, ecosystems are seen
as continually evolving with multiple potential stable states.
48) What determines the rates of primary succession and
secondary succession?
a) Primary Succession: Occurs in areas with no pre-existing soil or life,
such as after a volcanic eruption or glacial retreat. The rate is generally
slow and depends on:
i) Soil formation: The development of soil from bare rock through
processes like weathering and the activity of pioneer species (e.g.,
lichens, mosses).
ii) Availability of nutrients: Nutrient accumulation, often facilitated by
pioneer species, is crucial for plant and organism growth.
iii) Climate: Harsh conditions (e.g., extreme cold or dryness) can slow
the process, while milder conditions speed it up.
b) Secondary Succession: Occurs in areas where soil and some organisms
remain after a disturbance (e.g., fire, flood). The rate is typically faster
and influenced by:
i) Existing soil: Presence of soil allows plants to establish quickly,
speeding up recovery.
ii) Seed banks and surviving organisms: Seeds and root systems
remaining in the soil can sprout and regrow quickly.
iii) Nature of the disturbance: The severity of the disturbance (e.g.,
whether soil is intact) determines how quickly recovery occurs.
c) Overall, primary succession is slower due to the need to build soil and
establish a foundation for life, while secondary succession is faster
because of the pre-existing resources and organisms.
49) Is there an end to the process of succession? Explain/justify
your answer.
a) Succession is often thought of as a process that moves toward a stable
climax community, but modern ecology suggests that there is no true
end to succession. Ecosystems are dynamic and constantly influenced
by disturbances such as fires, storms, or human activity, which can
restart or alter the successional process. Additionally, factors like
climate change, species interactions, and environmental fluctuations
can continuously shape community composition.
b) While ecosystems may reach temporary periods of stability, ongoing
disturbances and environmental changes mean that succession is an
ongoing, cyclical process rather than having a permanent end. Thus,
ecosystems remain in a state of flux, with succession being part of
their natural dynamics.
50) Does a climax community exist? Explain/justify your answer.
a) The concept of a climax community, where an ecosystem reaches a
stable and unchanging state after succession, is now considered
outdated and overly simplistic. Ecosystems are dynamic and subject to
ongoing disturbances, such as fires, storms, and human activities, as
well as longer-term changes like climate shifts. These factors prevent
ecosystems from remaining in a fixed state.
b) While some ecosystems may appear stable for a time, they are
constantly influenced by external and internal factors, causing
continual shifts in species composition and community structure.
Therefore, a permanent, unchanging climax community does not truly
exist in most ecological contexts. Instead, ecosystems are seen as
evolving, with multiple potential stable states rather than one fixed
endpoint.
51) Explain and give an example of cyclic replacement.
a) Cyclic replacement refers to a process in which an ecosystem
undergoes recurring changes due to disturbances that reset or alter
the successional stages within a community, leading to a cycle of
growth, disturbance, and regrowth.
b) A classic example of cyclic replacement can be observed in grassland
ecosystems that experience periodic wildfires.
i) Fire Disturbance: When a wildfire occurs, it can remove the
dominant vegetation, such as mature grasses and shrubs, allowing
sunlight to reach the soil.
ii) Pioneer Species: Following the fire, pioneer species (e.g., annual
grasses and forbs) quickly colonize the area, taking advantage of
the nutrient-rich soil and available sunlight.
iii) Successional Growth: Over time, these pioneer species may be
replaced by more competitive perennial grasses and eventually
shrubs or young trees, leading to a more complex community
structure.
iv) Repeat of Disturbance: If another fire occurs, this process may start
again, resetting the community to earlier successional stages and
repeating the cycle.
c) This cyclic nature highlights how disturbances can shape community
dynamics and promote biodiversity over time.
52) Explain the shifting mosaic model.
a) The shifting mosaic model is an ecological concept that describes
ecosystems as dynamic landscapes consisting of patches at various
stages of ecological succession. Unlike traditional linear models of
 succession, which imply a predictable progression toward a climax
community, the shifting mosaic model emphasizes spatial and
temporal heterogeneity.
i) Dynamic Patches: Different areas within an ecosystem can be at
different stages of succession due to various disturbances (e.g., fire,
storms, herbivory) occurring at different times and locations.
ii) Continuous Change: As disturbances create new patches, some
areas may be recovering, while others are in early successional
stages or are more mature, resulting in a mosaic of habitats within
the same ecosystem.
iii) Biodiversity Support: This patchiness can enhance species diversity
by providing a variety of habitats and resources for different
species, allowing for a greater variety of life forms to coexist.
iv) Non-linear Dynamics: The model acknowledges that ecological
change is not a linear progression toward a fixed endpoint but a
complex, ongoing process influenced by both biotic and abiotic
factors.
b) Overall, the shifting mosaic model highlights the complexity of
ecosystems and the importance of disturbances in shaping community
structure and biodiversity over time.
53) The process of succession can go in two directions. Explain.
a) The process of succession can proceed in two main directions: primary
succession and secondary succession, each influenced by different
starting conditions and disturbances.
i) Primary Succession: This occurs in areas that have been completely
devoid of life, such as after a volcanic eruption or glacial retreat,
where there is no soil or organic matter. The process begins with
pioneer species, such as lichens and mosses, that colonize bare rock
and gradually help form soil. Over time, as soil develops, more
complex plant communities, including grasses, shrubs, and trees,
can establish themselves.
ii) Secondary Succession: This occurs in areas where a disturbance has
removed some or all of the existing vegetation but left the soil
intact, such as after a fire, flood, or human activity (e.g., logging).
Since the soil and some organisms remain, secondary succession
typically proceeds more quickly than primary succession. The
process begins with the regrowth of plants from seeds, root
systems, or vegetative fragments, leading to the reestablishment of
a more complex community over time.
 b) In summary, succession can move forward from bare ground to a
mature ecosystem (primary succession) or recover from a disturbance
while retaining soil and organisms (secondary succession),
demonstrating the adaptability and resilience of ecosystems.
54) The key to diversity of wildlife in a given area is the
maintenance of a heterogenous landscape with habitats of
various successional stages. Explain.
a) The maintenance of a heterogeneous landscape with habitats at
various successional stages is crucial for fostering biodiversity because
it provides a variety of niches and resources for different species.
i) Diverse Habitats: Different successional stages offer distinct
environmental conditions, such as varying light levels, moisture,
and soil nutrients. This diversity creates multiple habitats that can
support a wide range of plant and animal species, each adapted to
specific conditions.
ii) Resource Availability: A mosaic of habitats ensures that resources,
such as food and shelter, are available to different species at
various times. For example, early successional habitats may provide
abundant food for herbivores, while later stages may offer nesting
sites for birds.
iii) Increased Resilience: A heterogeneous landscape can enhance
ecosystem resilience, allowing it to better withstand disturbances. If
one area is affected by a disturbance (like fire or disease), other
areas may remain intact, helping to sustain overall wildlife
populations.
iv) Facilitation of Species Interactions: The variety of habitats promotes
interactions between species, such as predator-prey dynamics and
mutualistic relationships, contributing to a balanced ecosystem.
b) In summary, maintaining a heterogeneous landscape with diverse
habitats at different successional stages is essential for promoting
wildlife diversity, ensuring a stable and resilient ecosystem capable of
supporting various species.
55) Species diversity generally increases during succession.
Explain.
a) Species diversity generally increases during succession due to several
interrelated factors:
i) Habitat Development: As succession progresses, the environment
becomes more complex and diverse. Early stages may be
dominated by a few pioneer species, but as these species modify
the habitat (e.g., by improving soil quality, altering light levels), new
 niches become available, allowing for the colonization of additional
species.
ii) Resource Availability: With time, as more plant species establish,
there is a greater availability of resources such as food, shelter, and
habitat. This diversity of resources supports a wider range of
organisms, including herbivores, predators, and decomposers.
iii) Facilitation and Interactions: Some species help create conditions
that facilitate the growth of others. For instance, certain plants can
improve soil nutrients or provide shade, creating suitable conditions
for understory species. These interactions promote the
establishment of new species, enhancing overall diversity.
iv) Reduced Competition: In the early stages of succession, competition
may be limited due to the low number of species present. As more
species establish themselves, this competition can drive further
diversification as species adapt to exploit different resources or
niches.
b) Overall, as succession progresses, the gradual accumulation of species
and the development of complex interactions contribute to an increase
in species diversity within the ecosystem.
56) Explain how disturbances can affect species diversity.
a) Disturbances can significantly affect species diversity in various ways,
depending on their frequency, intensity, and type. Here’s how:
i) Creation of New Habitats: Disturbances, such as fires, floods, or
storms, can create new habitats by clearing out dominant
vegetation and opening space for new species to establish. This can
lead to an increase in diversity as pioneer species colonize the
disturbed area, followed by a succession of other species.
ii) Resilience and Adaptation: Disturbances can promote resilience in
ecosystems by encouraging a variety of species to adapt to
changing conditions. Species that can thrive under disturbance
conditions may flourish, while others may decline, leading to shifts
in community composition.
iii) Niche Availability: Disturbances can change resource availability,
creating new niches. This allows for different species to exploit
various resources, enhancing diversity as more organisms adapt to
occupy those niches.
iv) Species Interactions: Disturbances can alter interactions between
species, such as predator-prey dynamics and competition. These
changes can either enhance or reduce species diversity, depending
on how they affect survival and reproduction.
 v) Intermediate Disturbance Hypothesis: This ecological theory
suggests that moderate levels of disturbance can maximize species
diversity. Too little disturbance may lead to dominance by a few
competitive species, while too much disturbance can lead to local
extinctions and loss of diversity.
b) In summary, disturbances play a crucial role in shaping species
diversity by creating new opportunities for colonization, altering
species interactions, and facilitating the coexistence of various species
in an ecosystem.
57) Explain the equilibrium model of succession.
a) The equilibrium model of succession posits that ecosystems tend
toward a stable state or climax community, characterized by a
relatively constant composition of species and minimal change over
time, barring significant disturbances. This model suggests that
ecological processes and species interactions lead to a predictable
progression through distinct successional stages, ultimately resulting in
a stable community that can withstand minor disturbances.
i) Sequential Stages: Succession progresses through a series of stages
(pioneer, intermediate, climax) where each stage is dominated by
specific species that modify the environment, facilitating the
establishment of subsequent species.
ii) Climax Community: The climax community represents a stable
endpoint where species composition is balanced, and ecological
processes are in equilibrium. This community is thought to be in a
steady state, able to maintain itself over time unless disrupted by
significant disturbances.
iii) Resistance and Resilience: The equilibrium model emphasizes that
mature ecosystems have a degree of resistance to disturbances and
can return to the climax state following minor disruptions,
maintaining biodiversity and stability.
iv) Predictability: The model implies that the trajectory of succession is
relatively predictable, with specific pathways leading to the climax
community based on regional climate, soil type, and other
environmental factors.
b) While the equilibrium model provides a useful framework for
understanding successional dynamics, it is important to note that
many modern ecologists recognize that ecosystems are dynamic and
influenced by ongoing disturbances, leading to more complex and non-
linear patterns of change.
58) Explain the intermediate disturbance hypothesis.
 a) The intermediate disturbance hypothesis (IDH) posits that ecosystems
experiencing moderate levels of disturbance will support the highest
levels of species diversity. This concept suggests that both low and
high disturbance frequencies can lead to decreased diversity for
different reasons:
i) Low Disturbance: In environments with few disturbances, dominant
species tend to outcompete others, leading to decreased species
diversity. The lack of disturbances allows these competitive species
to monopolize resources, leaving little opportunity for less
competitive species to thrive.
ii) High Disturbance: Conversely, in areas with frequent or intense
disturbances, many species may be unable to establish or survive
due to constant upheaval. This can lead to a reduction in overall
species diversity as numerous species face local extinction.
iii) Optimal Disturbance: The IDH suggests that moderate disturbances
create a balance, preventing any single species from dominating
while allowing various species to establish and coexist. These
disturbances create openings in the habitat that can be colonized
by a wider range of species, increasing overall biodiversity.
b) In summary, the intermediate disturbance hypothesis highlights the
importance of disturbance dynamics in shaping community structure
and biodiversity, suggesting that a moderate level of disturbance
promotes a diverse and resilient ecosystem.
59) Discuss and give examples of normal barriers to the expansion
of species ranges.
a) Normal barriers to the expansion of species ranges are ecological and
environmental factors that limit the distribution of species. These
barriers can prevent populations from spreading into new areas,
impacting their ability to thrive. Here are some common examples:
i) Physical Barriers: Natural features such as mountains, rivers, and
oceans can hinder movement and dispersal. For example, a
mountain range may prevent a species from migrating to a suitable
habitat on the other side, limiting its range.
ii) Climate and Weather: Species have specific climatic tolerances. For
instance, a plant species adapted to warm, dry conditions may
struggle to survive in colder, wetter regions. Climate zones can thus
act as barriers to range expansion.
iii) Soil and Nutrient Availability: Soil type and nutrient content can
significantly affect plant distribution. For example, a species that
 requires specific soil nutrients may not thrive in regions with
nutrient-poor soils, restricting its range.
iv) Biological Barriers: Interactions with other species, such as
competition, predation, or parasitism, can limit the range of a
species. For example, a herbivore may be unable to expand its
range into areas where it faces strong competition from other
herbivores or predation from local carnivores.
v) Human Activity: Urbanization, agriculture, and habitat destruction
can create barriers for many species. For example, a road or city
can fragment habitats, making it difficult for species to move
between areas and thus limiting their range.
b) These barriers are important in shaping the distribution and diversity of
species across different ecosystems.
60) Describe the global clines in species diversity. Give examples.
a) Global clines in species diversity refer to the gradual changes in
species richness and diversity observed across different geographical
regions, often influenced by environmental factors such as climate,
latitude, and habitat type. Here are key features and examples of these
clines:
i) Latitudinal Gradient: Generally, species diversity tends to increase
as one moves from polar regions toward the equator. Tropical
regions, such as the Amazon rainforest, are known for their high
biodiversity, hosting thousands of plant and animal species. In
contrast, polar regions, like the Arctic tundra, have relatively low
species diversity due to harsh climatic conditions.
ii) Altitude: Similar to latitude, species diversity often decreases with
increasing altitude. For example, tropical mountains such as the
Andes or the Himalayas show high diversity at lower elevations,
which declines as one ascends due to factors like temperature,
oxygen availability, and habitat types.
iii) Habitat Heterogeneity: Areas with complex and varied habitats tend
to support higher species diversity. For example, coral reefs,
characterized by diverse physical structures, have one of the
highest levels of marine biodiversity compared to more
homogeneous environments like the open ocean.
iv) Seasonality and Stability: Regions with stable climates and distinct
seasons, such as Mediterranean ecosystems, can exhibit high
species diversity due to a variety of habitats and resources. In
contrast, regions with extreme seasonal fluctuations, like deserts,
may support fewer species.
 v) Human Influence: Human activities can also affect global clines in
species diversity. For example, deforestation and habitat
fragmentation in biodiverse regions, such as the Amazon, lead to
declines in species richness and threaten endemic species.
b) In summary, global clines in species diversity illustrate how ecological
and geographical factors interact to shape patterns of biodiversity
across different regions, with notable examples demonstrating these
trends in various ecosystems worldwide.
61) What drives the global clines in species diversity? Explain.
a) Global clines in species diversity are driven by a combination of
ecological, environmental, and evolutionary factors. Here are the main
drivers:
i) Latitude: The latitudinal gradient is one of the most significant
drivers of species diversity. Biodiversity generally increases toward
the equator due to warmer temperatures, more consistent sunlight,
and a greater variety of habitats. Tropical regions provide favorable
conditions for year-round growth and reproduction, supporting
higher species richness.
ii) Climate: Climate influences species diversity through temperature,
precipitation, and seasonality. Stable and mild climates support
diverse ecosystems, while extreme climates (e.g., deserts, polar
regions) limit species richness. For example, areas with high rainfall
and warm temperatures, such as tropical rainforests, exhibit high
biodiversity.
iii) Habitat Heterogeneity: The complexity and variety of habitats within
a region can significantly impact species diversity. Regions with
diverse habitats, such as mountains or coral reefs, provide
numerous niches for different species, leading to increased
biodiversity.
iv) Evolutionary History: Historical factors, such as past climate
changes, glaciation events, and geographical isolation, shape
species diversity. Areas that have remained stable for long periods
(e.g., tropical forests) tend to have higher species richness
compared to regions that have experienced frequent disturbances.
v) Species Interactions: Ecological interactions, including competition,
predation, and mutualism, play a crucial role in shaping biodiversity.
These interactions can drive speciation and influence community
structure, contributing to the overall diversity within ecosystems.
vi) Human Impact: Anthropogenic factors, such as habitat destruction,
climate change, and pollution, can alter species distributions and
 lead to declines in biodiversity. The introduction of invasive species
can also disrupt existing communities, affecting native species
diversity.
b) In summary, global clines in species diversity are influenced by a
complex interplay of latitude, climate, habitat heterogeneity,
evolutionary history, species interactions, and human activities, all of
which shape the distribution and richness of species across different
ecosystems.
62) EXPLAIN what determines the final number of species that
inhabit and “island.”
a) The final number of species that inhabit an "island" is determined by a
combination of factors outlined in the Equilibrium Theory of Island
Biogeography. This theory posits that species richness on islands is
influenced by the balance between immigration and extinction rates.
Key determinants include:
i) Size of the Island: Larger islands generally support more species
than smaller islands due to greater habitat diversity, availability of
resources, and lower extinction rates. Larger areas can sustain
larger populations, reducing the likelihood of extinction.
ii) Distance from the Mainland: Islands that are closer to a mainland
source of colonizing species typically have higher immigration rates.
The farther an island is from the mainland, the fewer species are
likely to arrive, leading to lower species richness.
iii) Habitat Diversity: The variety of habitats available on the island can
support more species by providing different niches. Islands with
diverse ecosystems (e.g., varied topography, climates, and
vegetation) can accommodate a wider range of species.
iv) Ecological Interactions: Species interactions, such as competition,
predation, and mutualism, can influence community dynamics and
affect both immigration and extinction rates. High competition may
limit the number of species that can coexist.
v) Disturbance Events: Natural disturbances (like hurricanes or
volcanic eruptions) can alter the island's environment, affecting
species richness by causing extinctions or creating new habitats for
colonization.
vi) Human Impact: Human activities, such as habitat destruction and
the introduction of invasive species, can drastically influence
species richness on islands by increasing extinction rates and
altering ecological dynamics.
 b) In summary, the final number of species inhabiting an island is
determined by the interplay of island size, distance from the mainland,
habitat diversity, ecological interactions, disturbance events, and
human impacts, all of which shape the rates of immigration and
extinction.
63) Explain what determines/influences the rate of immigration to
new “islands.”
a) The rate of immigration to new "islands" is influenced by several key
factors:
i) Distance from the Source Population: The closer an island is to a
mainland or source of potential colonizers, the higher the
immigration rate. Proximity facilitates easier dispersal of organisms,
increasing the likelihood of species reaching the island.
ii) Size of the Island: Larger islands typically attract more immigrants
than smaller ones due to a greater availability of habitats and
resources. They can support larger populations, which can further
enhance immigration rates.
iii) Habitat Diversity: Islands with diverse habitats offer more niches for
colonizing species, making them more attractive for immigrants.
The presence of various microhabitats can also support a wider
range of organisms.
iv) Species Characteristics: The dispersal abilities of different species
play a significant role in immigration rates. Some species are better
adapted to long-distance dispersal (e.g., birds, wind-dispersed
seeds), while others may have limited dispersal capabilities.
v) Environmental Conditions: Favorable environmental conditions, such
as appropriate climate and availability of resources (e.g., food and
nesting sites), can enhance the likelihood of successful colonization
and increase immigration rates.
vi) Ecological Interactions: Interactions with existing species on the
island, such as competition and predation, can influence the
success of incoming immigrants. If established species are highly
competitive, they may limit the ability of new species to immigrate
and establish.
vii) Human Influence: Human activities, such as habitat destruction
and the introduction of invasive species, can also affect immigration
rates. Disturbances may either facilitate the arrival of new species
or hinder the natural colonization process.
b) In summary, the rate of immigration to new islands is influenced by the
distance from source populations, island size, habitat diversity, species
 characteristics, environmental conditions, ecological interactions, and
human impacts, all of which collectively shape the dynamics of
colonization.
64) Explain the process and forces involved in colonizing a new
island.
a) The process of colonizing a new island involves several key stages and
forces, which can be summarized as follows:
i) Dispersal: The initial step in colonization is the dispersal of
organisms from a source population to the island. Dispersal can
occur through various means, including wind, water currents, animal
movement, or human activity. The ability of species to travel long
distances greatly influences the success of colonization.
ii) Arrival and Establishment: Once organisms reach the island, they
must find suitable habitats and resources for survival. This process
includes locating food, water, and nesting sites. Species that are
well-adapted to the island's environmental conditions are more
likely to establish themselves successfully.
iii) Biotic Interactions: After arrival, newly colonizing species engage in
biotic interactions with existing organisms on the island. These
interactions include competition for resources, predation, and
mutualism. The outcome of these interactions can determine
whether the newcomers thrive or struggle to survive.
iv) Environmental Adaptation: Colonizing species may undergo
adaptations to better fit the new environment. This process can lead
to changes in morphology, behavior, or reproductive strategies that
enhance their ability to exploit available resources.
v) Population Growth: If conditions are favorable and resources are
abundant, the newly established populations can grow, potentially
leading to increased species richness on the island. However,
population growth may also attract competition and predation,
which can regulate species abundance.
vi) Stabilization and Community Development: Over time, the
colonization process leads to the stabilization of the community
structure. Species interactions can lead to the establishment of a
balanced ecosystem, where different species coexist and contribute
to the overall biodiversity.
vii) Disturbances: Natural disturbances (e.g., storms, volcanic
activity) can create opportunities for further colonization by
resetting ecological succession. Disturbances can also influence
which species dominate the ecosystem.
 b) In summary, colonizing a new island involves dispersal, establishment,
biotic interactions, environmental adaptation, population growth,
stabilization, and response to disturbances. These processes and forces
shape the dynamics of species colonization and community
development in island ecosystems.
65) According to the theory of island biogeography, explain what
determines the number of species found on an island.
a) According to the Theory of Island Biogeography, the number of species
found on an island is determined by the balance between immigration
and extinction rates, influenced by several key factors:
i) Island Size: Larger islands can support more species due to greater
habitat diversity and resources. They generally have lower
extinction rates because larger populations can sustain themselves
better and have a reduced likelihood of local extinction.
ii) Distance from the Mainland: The distance of the island from a
source of colonizing species (such as the mainland) affects
immigration rates. Closer islands receive more immigrants, resulting
in a higher potential species richness compared to more distant
islands.
iii) Habitat Diversity: Islands with diverse habitats (e.g., different
ecosystems, vegetation types) can support a wider range of
species. More available niches increase the likelihood of successful
colonization and coexistence of different species.
iv) Species Interactions: Competition, predation, and mutualism among
species can influence both immigration and extinction rates.
Established species can affect the survival of newcomers, while new
arrivals can also alter existing dynamics within the community.
v) Ecological Dynamics: The equilibrium number of species is reached
when the rate of immigration equals the rate of extinction. As more
species establish themselves on the island, competition for
resources increases, leading to higher extinction rates. Conversely,
if few species are present, immigration rates tend to be higher.
b) In summary, the number of species on an island is determined by the
interplay of island size, distance from source populations, habitat
diversity, ecological interactions, and the dynamic balance between
immigration and extinction rates, all of which shape species richness in
island ecosystems.
66) Number of bird species on various island of the east indies in
relation to area.
 a) The number of bird species on various islands in the East Indies
generally demonstrates a positive correlation with the area of the
islands. This relationship is consistent with the Theory of Island
Biogeography, which suggests that larger islands can support more
species due to several factors:
i) Habitat Diversity: Larger islands typically offer a greater variety of
habitats, allowing for more ecological niches that can accommodate
diverse bird species.
ii) Population Size: Larger areas can support larger populations, which
decreases the likelihood of extinction due to demographic
fluctuations and environmental changes.
iii) Colonization Opportunities: Bigger islands are often more attractive
to potential colonizers due to their size and the resources they offer,
leading to higher immigration rates.
iv) Distance from Mainland: The effect of distance also plays a role;
islands that are both large and relatively close to the mainland tend
to have higher bird species richness compared to smaller or more
isolated islands.
b) In summary, within the East Indies, larger islands generally host a
greater number of bird species, reflecting the interplay of habitat
availability, population sustainability, and colonization dynamics,
consistent with principles of island biogeography.

67)
a) Immigration – colonization of NEW species
b) Extinction – species being eliminated from the island
c) S – Number of species on the island at equilibrium
68) How do organisms interact with each of these abiotic factors?
Climate, Temperature, Water, Light, Nutrients, Soil, Wind, and
Disturbances.
a) Organisms interact with abiotic factors in various ways, influencing
their survival, growth, and reproduction. Here's a brief overview of how
organisms interact with each of the specified abiotic factors:
i) Climate: Organisms adapt to specific climatic conditions (e.g.,
temperature, humidity, and seasonal variations). For instance, cacti
are adapted to arid climates, while amphibians thrive in moist
environments. Climate influences species distribution and behavior,
such as migration patterns in birds.
ii) Temperature: Temperature affects metabolic rates, growth, and
reproduction. Organisms have specific temperature tolerances; for
example, cold-blooded animals (ectotherms) regulate their body
temperature through environmental conditions, while warm-blooded
animals (endotherms) maintain a constant internal temperature.
iii) Water: Water availability is crucial for survival. Aquatic organisms,
like fish, depend on water for habitat, while terrestrial plants have
adaptations (like deep roots or waxy surfaces) to conserve moisture.
Drought conditions can limit the distribution of certain plant species.
iv) Light: Light is essential for photosynthesis in plants and algae.
Different species have varying light requirements; shade-tolerant
plants thrive in low-light environments, while sun-loving plants
prefer direct sunlight. Light also influences animal behavior, such as
nocturnal versus diurnal activity patterns.
v) Nutrients: Nutrient availability affects growth and productivity.
Plants require essential nutrients (e.g., nitrogen, phosphorus) from
the soil, while animals obtain nutrients through their diet. Depleted
nutrient levels can limit plant growth, impacting entire food webs.
vi) Soil: Soil composition and structure influence plant growth and
nutrient availability. Different plant species are adapted to various
soil types (e.g., sandy, clay, loamy). Soil quality affects water
retention and root penetration, impacting the overall health of
terrestrial ecosystems.
vii) Wind: Wind can influence temperature and moisture levels,
affecting plant transpiration and water loss. Strong winds can
physically damage plants and impact animal movement and
behavior. In coastal areas, wind also plays a role in seed dispersal
for some plant species.
 viii) Disturbances: Disturbances (e.g., fires, storms, floods) can alter
habitats and influence species dynamics. Some species are adapted
to thrive after disturbances (e.g., fire-adapted plants), while others
may be vulnerable to habitat destruction. Disturbances can create
opportunities for new species to establish.
b) In summary, organisms interact with abiotic factors through
adaptations, behaviors, and ecological relationships, which collectively
shape their survival and distribution within ecosystems.
69) What is the lowest trophic level for all ecosystems?
a) The lowest trophic level in all ecosystems is occupied by producers,
also known as autotrophs. These organisms, which include plants,
algae, and certain bacteria, convert inorganic materials into organic
matter through processes like photosynthesis or chemosynthesis.
b) Producers are essential for ecosystems because they form the
foundation of the food web, providing energy and nutrients for higher
trophic levels, such as herbivores (primary consumers) and predators
(secondary and tertiary consumers). By capturing energy from the sun
or inorganic compounds, producers enable the flow of energy through
the ecosystem and support the diverse array of life that depends on
them.
70) Give an example of an organism that can feed at two different
trophic levels. Explain.
a) An example of an organism that can feed at two different trophic levels
is the American black bear (Ursus americanus). Black bears are
considered omnivores, meaning they consume both plant and animal
matter, allowing them to occupy multiple trophic levels.
i) Primary Consumer: As herbivores, black bears feed on various plant
materials, including berries, nuts, roots, and vegetation. In this role,
they function as primary consumers, obtaining energy directly from
producers (plants).
ii) Secondary Consumer: In addition to their herbivorous diet, black
bears also hunt and scavenge for animal protein, such as insects,
fish (like salmon), and small mammals. In this capacity, they act as
secondary consumers, feeding on organisms that are primary
consumers or other lower-level carnivores.
b) This flexibility in diet allows black bears to adapt to seasonal changes
and the availability of food resources, making them resilient in various
environments. Their ability to occupy different trophic levels plays a
crucial role in the ecosystem, influencing both plant and animal
populations.
71) Explain what happens to energy as you go up the trophic
levels.
a) As you go up the trophic levels in an ecosystem, energy is
progressively lost due to several factors, primarily outlined by the 10%
rule in ecology. Here's how the energy dynamics work:
i) Energy Transfer: When energy is transferred from one trophic level
to the next (e.g., from producers to primary consumers), only about
10% of the energy is converted into biomass. This means that
approximately 90% of the energy is lost at each level, primarily as
heat through metabolic processes, movement, and respiration.
ii) Decreased Energy Availability: As a result of this energy loss, higher
trophic levels have less energy available to support organisms. For
example, if producers (plants) capture 1,000 units of energy through
photosynthesis, only about 100 units may be available to primary
consumers (herbivores), and about 10 units to secondary
consumers (carnivores) that eat those herbivores.
iii) Decreased Biomass and Population Size: The loss of energy at each
trophic level also leads to a decrease in the total biomass and
population sizes of organisms as you move up the food chain. Fewer
individuals can be supported at higher trophic levels due to the
limited energy available.
iv) Impact on Ecosystem Structure: This energy loss affects the overall
structure and dynamics of the ecosystem, leading to a pyramid
shape when visualizing trophic levels, with a wide base of producers
and progressively narrower levels of consumers.
b) In summary, as you ascend trophic levels, energy availability
decreases significantly, resulting in fewer organisms and lower
biomass at higher levels due to the inefficiencies in energy transfer.
72) Explain the shape of a trophic pyramid and the size of each
level.
a) The shape of a trophic pyramid is typically pyramidal, with a broad
base that tapers toward the top. This shape represents the distribution
of energy, biomass, or number of organisms at each trophic level in an
ecosystem.
i) Base of the Pyramid (Producers): The widest part of the pyramid
consists of producers (autotrophs), such as plants and algae. This
level has the largest biomass and energy content because it
captures solar energy through photosynthesis and forms the
foundation for all other trophic levels.
 ii) Primary Consumers: Above the producers are primary consumers
(herbivores), which have a smaller biomass and energy availability
than the producers. The size of this level is narrower than the base
due to the loss of energy (approximately 90%) as it is transferred
from producers to primary consumers.
iii) Secondary Consumers: This level consists of secondary consumers
(carnivores that eat herbivores) and is even smaller than the
primary consumer level. Again, energy loss contributes to this
reduced size.
iv) Tertiary and Higher-Level Consumers: Higher trophic levels, such as
tertiary consumers (predators that eat other carnivores), continue
to decrease in size, reflecting the diminishing energy availability as
you move up the pyramid.
b) In summary, the trophic pyramid's shape illustrates the decreasing
biomass, energy, and number of organisms at each successive trophic
level, resulting in a broad base of producers that narrows at the top
with fewer higher-level consumers. This structure emphasizes the
inefficiencies in energy transfer through the ecosystem.
73) Construct a figure showing four different trophic levels found
in a temperate deciduous forest. Label each feeding level, give
the type of feeder at each level, and finally, give an actual
example of an organism at each level.

a)
b) Producers: Oak trees.
c) Primary consumers: White-tailed deer (herbivores).
d) Secondary consumers: Red foxes (small carnivores).
e) Tertiary consumers: Great horned owls (apex predators).
74) What is the highest level of all trophic levels? Give examples
of organisms found in this level.
a) The highest level of all trophic levels is known as the quaternary
consumer level, which consists of apex predators that have no natural
predators of their own. These organisms occupy the top of the food
chain and play a crucial role in regulating the populations of species in
lower trophic levels.
i) Great White Shark (Carcharodon carcharias): As a top predator in
marine ecosystems, the great white shark preys on a variety of
marine animals, including seals, fish, and other sharks.
ii) African Lion (Panthera leo): Known as a keystone species in savanna
ecosystems, lions hunt large herbivores such as zebras and
wildebeests, helping to maintain ecological balance.
iii) Bald Eagle (Haliaeetus leucocephalus): This bird of prey is an apex
predator in its habitat, feeding on fish and small mammals, and
plays a vital role in controlling prey populations.
iv) Polar Bear (Ursus maritimus): As the top predator in the Arctic, polar
bears primarily hunt seals and are crucial for maintaining the
balance of the marine ecosystem in their habitat.
b) In summary, quaternary consumers are the highest trophic level and
include apex predators like great white sharks, African lions, bald
eagles, and polar bears, which have significant impacts on their
ecosystems through their predatory behaviors.
75) What are the most dominate primary producers in the
terrestrial and aquatic ecosystems?
a) Terrestrial Ecosystems:
i) Plants: Vascular plants, particularly angiosperms (flowering plants)
and gymnosperms (conifers), are the most dominant primary
producers. They capture solar energy through photosynthesis and
are critical for providing food and habitat for herbivores and other
organisms in terrestrial environments.
b) Aquatic Ecosystems:
i) Phytoplankton: In aquatic ecosystems, particularly in oceans and
freshwater environments, phytoplankton (microscopic
photosynthetic organisms) are the dominant primary producers.
They include various types of algae and cyanobacteria, which form
the foundation of the aquatic food web by converting sunlight and
nutrients into organic matter through photosynthesis.
c) In summary, vascular plants dominate primary production in terrestrial
ecosystems, while phytoplankton serve as the primary producers in
 aquatic ecosystems, both playing vital roles in energy flow and nutrient
cycling within their respective environments.
76) How does primary production occur in ecosystems where there
is not light?
a) In ecosystems where there is no light, such as deep-sea environments,
hydrothermal vents, and some underground ecosystems, primary
production occurs through a process called chemosynthesis. This
process is carried out by certain bacteria and archaea that can convert
inorganic molecules into organic matter without relying on sunlight.
i) Energy Source: Chemosynthetic organisms use energy derived from
the oxidation of inorganic compounds, such as hydrogen sulfide
(H₂S), methane (CH₄), or ammonia (NH₃). This energy is harnessed
to convert carbon dioxide (CO₂) and water into organic compounds.
ii) Chemosynthetic Bacteria: For example, at hydrothermal vents,
chemosynthetic bacteria oxidize hydrogen sulfide released from the
vent to produce glucose and other organic molecules, which serve
as food for various organisms, including giant tube worms, clams,
and other vent-associated species.
iii) Ecosystem Support: Chemosynthetic primary production supports
unique ecosystems that thrive in extreme conditions, independent
of sunlight. These ecosystems often feature complex food webs
built around chemosynthetic organisms, allowing life to persist in
environments that would otherwise be inhospitable.
b) In summary, primary production in the absence of light occurs through
chemosynthesis, where specific microorganisms convert inorganic
compounds into organic matter using energy from chemical reactions,
supporting life in dark and extreme environments.
77) Distinguish between primary and secondary production. Give
an example of each.
a) Primary Production:
i) Definition: Primary production refers to the generation of organic
matter (biomass) by primary producers (autotrophs) through the
process of photosynthesis or chemosynthesis. It represents the
amount of solar or chemical energy converted into chemical energy
in the form of organic compounds.
ii) Example: In a temperate forest, trees, shrubs, and grasses convert
sunlight into energy through photosynthesis, resulting in the growth
of biomass, which serves as the foundation of the food web.
b) Secondary Production:
 i) Definition: Secondary production refers to the generation of biomass
by heterotrophic organisms (consumers) that obtain their energy by
consuming primary producers or other consumers. It reflects the
conversion of organic matter into consumer biomass.
ii) Example: In the same temperate forest ecosystem, a deer
(herbivore) that feeds on the leaves and fruits of trees is an
example of secondary production. The energy and nutrients
obtained from the plants are used to grow and reproduce,
contributing to the overall biomass of the consumer level.
c) In summary, primary production involves the creation of biomass by
producers through photosynthesis or chemosynthesis, while secondary
production involves the generation of biomass by consumers that eat
primary producers or other consumers.
78) What are the primary consumers in the terrestrial and aquatic
ecosystems?
a) Primary consumers are organisms that feed directly on primary
producers (autotrophs) in an ecosystem, obtaining their energy by
consuming plant material or phytoplankton.
i) Terrestrial Ecosystems:
(1)Herbivores: In terrestrial ecosystems, primary consumers include
a variety of herbivorous animals. Examples include:
(a) Deer: They feed on grasses, leaves, and fruits.
(b)Grasshoppers: These insects consume grass and other
vegetation.
(c) Rabbits: They eat a range of plant materials, including herbs
and shrubs.
ii) Aquatic Ecosystems:
(1)Zooplankton: In aquatic ecosystems, primary consumers are
often represented by small organisms that feed on
phytoplankton. Examples include:
(a) Copepods: Tiny crustaceans that consume phytoplankton in
marine and freshwater environments.
(b)Daphnia: Commonly known as water fleas, these small
crustaceans feed on algae and other microscopic plants.
b) In summary, primary consumers in terrestrial ecosystems are typically
herbivorous animals like deer and rabbits, while in aquatic ecosystems,
they are often represented by zooplankton such as copepods and
Daphnia that feed on phytoplankton.
79) Give three detritivores. Explain/justify as needed. A grazer
eating living grass would not be a detritivore. Their food is
living. Humans don’t generally eat dead plant matter.
a) Detritivores are organisms that obtain their nutrients by consuming
dead organic matter, such as decomposing plant and animal material.
They play a crucial role in nutrient cycling and decomposition within
ecosystems. Here are three examples of detritivores:
i) Earthworms: Earthworms consume decaying leaves, dead plant
material, and organic matter in the soil. As they burrow, they help
aerate the soil and break down organic matter into smaller
particles, enhancing nutrient availability for plants.
ii) Woodlice (Pillbugs): Woodlice feed on decaying wood, leaf litter, and
other organic debris. By breaking down this material, they
contribute to the decomposition process and nutrient cycling in
terrestrial ecosystems.
iii) Fungi: While not traditionally classified as animals, fungi (such as
mushrooms) decompose dead organic material by breaking it down
into simpler compounds. They play an essential role in nutrient
recycling by converting complex organic matter into forms that can
be utilized by plants and other organisms.
b) In summary, detritivores like earthworms, woodlice, and fungi consume
dead organic matter, facilitating decomposition and nutrient cycling in
ecosystems, which distinguishes them from grazers that consume
living plant material.
80) Trophic pyramids don’t show the specifics of who is eating
whom. Food chains take examples of organisms at each trophic
levels and specifically show who is eating whom.
a) Trophic pyramids and food chains are both important concepts in
ecology that illustrate the flow of energy and matter through
ecosystems, but they serve different purposes.
i) Trophic Pyramids:
(1)Trophic pyramids represent the relative biomass, energy, or
number of organisms at each trophic level in an ecosystem,
typically arranged in a pyramid shape with primary producers at
the base and top predators at the apex.
(2)While they provide a broad overview of the structure of an
ecosystem and the decreasing energy availability at higher
trophic levels, they do not detail the specific interactions
between different species or illustrate the complex feeding
relationships.
 ii) Food Chains:
(1)Food chains, on the other hand, provide a linear sequence that
explicitly shows who eats whom within an ecosystem. They trace
the flow of energy from primary producers through various levels
of consumers, detailing the direct feeding relationships between
specific organisms.
(2)For example, a food chain might show that grass (producer) is
eaten by a grasshopper (primary consumer), which is then
consumed by a frog (secondary consumer), and subsequently
eaten by a snake (tertiary consumer).
b) In summary, while trophic pyramids provide a generalized view of
energy distribution among trophic levels, food chains offer specific
examples of feeding relationships, detailing the interactions between
organisms at each level.

81)
a) Terrestrial – highest net primary productivity is in the tropical
rainforests
b) Oceanic – highest near continents and lowest in the open seas; cooler
open water = higher productivity ; costal receives input from terrestrial
82)
a) Notice – in general, only 10% of the energy that enters one trophic
level is passed on the next higher level.

83)
a) About 40% wend directly into the leaves.
b) 13% washed out in rain.
c) 36% lost to leaf fall.
d) 51% returned to the wood.
84) Pyritic – rock containing iron pyrite