COURSE: GENERAL BIOLOGY

SUB COURSE: INTRODUCTION TO ECOLOGY AND REPRODUCTION

COURSE CODE: BIO101
COURSE LECTURER: YUSUF MOHAMMED
Definition of ecology
 The term “ecology” comes from the Greek, where “oikos” means “house” or “dwelling” and
“logos” means “study” or “science”. Thus, “ecology” essentially means the 'study of the household
of nature', or the study of a living place.
 Ecology is the scientific study of the interactions between organisms and their environments,
including both living and non-living components.
 Ecology involves examining the relationships between organisms and the physical, chemical and
biological factors that influence their distribution, abundance, and behavior.
Elements of ecology
The scope of ecology is huge, and it encompasses all organisms living on Earth and their physical and
chemical surrounding. For this reason, the field is usually divided into different levels of study, including
individual ecology, population ecology, community ecology and ecosystem ecology, among others.
Individual Ecology
 Organism is an individual living being that has the ability to act or function independently. It may be
plant, animal or fungi.
 Individual ecology looks at how individuals interact with their environment, which is made up
of biotic (living) and abiotic (non-living) components.
 The individual level in ecology refers to a single organism of a particular species. It involves
studying the characteristics, behaviors, and adaptations of an individual organism within its
environment.
 Physiological Adaptations: The individual level involves understanding how organisms are adapted
to survive and function within their environment. Camel, for example, develops physiological
features like a hump for water storage and specialized kidneys for water conservation in camels
living in arid regions. At the same time, when alligator is hunting - especially during cooler or
cloudy days – it will move very slowly and is able to hold its breath underwater for almost an hour
waiting for its prey.
 Behavioral Adaptations: Individual organisms exhibit behaviors that enhance their survival and
reproduction. For instance, honeybees perform elaborate dances to communicate the location of food
sources to other members of the hive. Also, because an alligator is cold-blooded, it needs to
maximize daylight hours absorbing heat from the sun, so it hangs out on the swamp banks soaking
up the rays.
 Morphological adaptation: Alligators have developed eyes and a nose on the top of their heads so
they can hide just below the surface while still being able to look out for prey and predators.
 Reproductive Strategies: The individual level involves understanding how organisms reproduce
and care for their offspring. Female sea turtles, for example, returns to specific beaches to lay eggs in
nests, contributing to the next generation.

Population Ecology

 A population is a group of individuals of the same species that share a common geographical area at
a given time and can potentially interbreed. They use the same natural resources and are affected by
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 similar environmental factors. Population ecology examines the factors affecting population size,
density and distribution.
 Population size is represented by the letter N, which refers to the total number of individual
organisms in a population.
 Population density is the number of individual organism per unit area or volume. A low density
region would have more spread of organisms whereas, a high density region would have more
individual organisms residing closer together, leading to greater resources competition.
 Population distribution refers to the spatial arrangement of individuals within a population. Some
populations may be clumped, uniform, or randomly dispersed based on the distribution of resources
and environmental conditions. Basically it is how populations change over time. For example, what
would happen to the alligator population in the swamp if the catfish population decreased due to
disease, or if a new competing predator is introduce.
 Population Dynamics: Population ecology explores the changes in the size, density, age structure,
and distribution of a population over time. Factors influencing population dynamics include birth
rates, death rates, immigration, and emigration.
 Population Structure: Population structure involves the composition of a population based on
factors such as age, sex, and reproductive status. This information is vital for understanding the
potential for population growth and the distribution of resources.
 Population Growth: The population growth rate is the % variation between the numbers of
individual in a population at two different times. Factors like birth rates, death rates, immigration,
emigration and reproductive strategies contribute to the overall growth rate.
 Population Regulation: Ecologists study the mechanisms that regulate population size, including
factors like predation, disease, availability of food, and environmental conditions. These factors
help maintain a balance within ecosystems.

Community Ecology

 A biological community is made up of two or more populations of different species inhabiting a

particular geographic area.
 In order to survive, individual of any one species depend on individual of different species with
which they actively interact.
 Food webs illustrate the complex network of feeding relationships within a community. They depict
the flow of energy and nutrients through various trophic levels, demonstrating the
interconnectedness of species. Let's consider the alligator and the swamp food web as an example.
 In this swamp community, the alligator is the top predator. It competes with the heron and the
snapping turtle for food because they all share snacks (catfish and invertebrates). However, the
alligator also preys on the heron and turtle.
 The duck, catfish, invertebrates and snake are all primary consumers. This is because they are
herbivores and they eat the plants, which are producers in the food chains.
 The nematodes at the bottom of the food web serve as detritivores. Detritivores clean up (eat) dead
matter at the bottom of the swamp.
 Community is named after dominant species, a grassland community, for instance, is occupied by
herbs, shrubs, trees and grasses. However, it is named after grass basically because it is dominated
by grasses.
 Community level studies often explore species richness (the number of species) and species
evenness (the distribution of individuals among species). A diverse community includes a variety of
species with different roles and functions.
 Disturbance and Resilience: Communities may face disturbances, such as fires, floods, or human
activities. Community ecology examines how communities respond to and recover from these
disturbances, emphasizing resilience and stability.

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Ecosystem Ecology

 An ecosystem is a structural and functional unit of biosphere, consisting of a various community of

organisms and environments both interacting and exchanging materials between them.
 Ecosystems can range from small ponds to vast forests, and they demonstrate the interconnectedness
of living and non-living components. If one part of the ecosystem is damaged, the whole system will
be disturbed but if ecosystem is healthy everything live in a balance and therefore can be able to
reproduce.
 Components of an Ecosystem:
i. Biotic Components: All living organisms, including plants, animals, fungi, and
microorganisms.
ii. Abiotic Components: Non-living factors such as air, water, soil, sunlight, energy and
minerals.
 Ecosystem Processes:
i. Energy Flow: Sunlight is captured by plants through photosynthesis, and this energy is
transferred through the ecosystem as organisms consume one another.
ii. Nutrient Cycling: Nutrients like carbon, nitrogen, and phosphorus cycle through the ecosystem
as living organisms die and decompose.
iii. Homeostasis: ecosystem is capable of regulating itself, such as purification of water and air by
wetlands and forests, pollination of plants by bees, and decomposition of wastes by
decomposers.
 Trophic Levels – Grassland Ecosystem
a. Producers: Autotrophic organisms (usually plants) that produce their own food through
photosynthesis. For example grasses and other plants.
b. Consumers: Heterotrophic organisms that consume other organisms for energy. These include
herbivores (e.g., deer, rabbits), carnivores (e.g., wolves, lions), omnivores (e.g., humans).
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 c. Decomposers: Organisms that break down dead organic matter, releasing nutrients back into
the ecosystem. E.g. Bacteria, fungi.
 The rate of decomposition is governed by three sets of factors;
a) The physical environment (temperature, moisture, and soil properties),
b) The quantity and quality of the dead material available to decomposers,
c) The nature of the microbial community.
 ECOTONE: This is a transitional area or junction between two or more different ecosystems,
supporting diverse and specialized flora and fauna. Examples include, grassland (forest and desert),
mangrove (land and aquatic system), and estuary (river and sea).
 The species composition or population density of some species is much greater in this zone than
adjoining communities. This is called edge effect.
 The distinct organisms which occupy primarily or most abundantly in this zone is termed edge
species.
 NICHE: This is a unique functional role or place of a species within an ecosystem. It includes a
range of conditions, resources, and interactions that a species need in order to survive, stay healthy,
and reproduce.
 A niche encompasses both the physical, chemical and biological aspects of an organism’s
environment such as its habitat, diet, reproductive behavior, and its interactions with other
species. Each species occupies a unique ecological niche, and these niches collectively contribute to
the balance and diversity of an ecosystem.
Types of Habitats
A habitat is a specific environment or area where an organism or a community of organisms lives. It
provides the necessary conditions, such as food, water, shelter, and suitable climate, for the survival,
growth, and reproduction of living organisms. Habitats vary widely, but some common types include
forests, deserts, grasslands, tundras, wetlands, and oceans. Each supports unique ecosystems and species
adapted to their specific environmental conditions.
1. Forests: A forest is a large area covered chiefly with trees and undergrowth. It’s a complex
ecosystem with diverse plant and animal life. Forests play a crucial role in maintaining biodiversity,
regulating climate, and providing various ecosystem services. Forests contribute significantly to
oxygen production, carbon sequestration, and supporting countless species in their habitats.
 Types: Tropical rainforests, temperate forests, boreal forests.
 Characteristics: Dense vegetation, diverse plant and animal species.
2. Deserts: A desert Is a biome characterized by arid conditions, typically receiving very low
precipitation. Deserts can be hot or cold and are often characterized by sparse vegetation and unique
adaptations of flora and fauna to conserve water. Despite their harsh conditions, deserts are home to
various resilient species that have evolved to thrive in the arid environment.
 Types: Hot deserts (e.g., Sahara), cold deserts (e.g., Gobi).
 Characteristics: Low precipitation, extreme temperature fluctuations.
3. Grasslands:
 Types: Savannas, prairies, steppes.
 Characteristics: Dominated by grasses, periodic wildfires, diverse herbivores.
4. Tundras: The tundra is a biome characterized by harsh environmental conditions, including low
temperatures, short growing seasons, and a lack of trees. It is found in the Arctic and alpine regions.
The Arctic tundra is located around the North Pole, while alpine tundra is found at high elevations on
mountains. The soil in tundra regions is often permanently frozen, a condition known as permafrost.
Vegetation in the tundra is adapted to the cold climate and typically consists of low-growing plants

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 like mosses, lichens, and dwarf shrubs. Tundras are home to hardy animals such as reindeer, polar
bears, and various migratory birds.
 Types: Arctic and alpine tundras.
 Characteristics: Cold, permafrost, low vegetation, adapted fauna.
5. Wetlands: A wetland is an area of land where the soil is saturated with water, either permanently or
seasonally. Wetlands include various environments such as marshes, swamps, and bogs. They play
crucial roles in supporting biodiversity, providing habitat for numerous plant and animal species.
Wetlands also contribute to water purification, flood control, and act as nurseries for fish. Due to their
ecological importance, wetlands are often protected to preserve their unique ecosystems and the
services they provide.
 Types: Marshes, swamps, bogs.
 Characteristics: Saturated or flooded soil, diverse aquatic plants, crucial for biodiversity.
6. Oceans:
 Types: Pelagic (open ocean), benthic (ocean floor), intertidal zones.
 Characteristics: Vast and diverse marine life, influenced by depth and currents.
Interrelationship of organisms
Organisms in ecosystems interact with each other in various ways, forming complex interrelationships.
Some common types of interactions include:
A. Predation: One organism (predator) consumes another organism (prey). For example, lions hunting
zebras on the African savanna.
B. Competition: Organisms compete for limited resources such as food, water, and territory. For
instance, plants competing for sunlight and nutrients in a forest.
C. Symbiosis: Close and long-term interaction between different species, which can be beneficial,
harmful, or neutral. Examples: Mutualism (both benefit), Parasitism (one benefits, the other is
harmed), Commensalism (one benefits, the other is unaffected).
D. Mutualism: Both organisms involved benefit from the interaction. Example, bees and flowers –
bees get nectar, while flowers get pollinated.
E. Parasitism: One organism (parasite) benefits at the expense of the host organism. For example, tick
feeding on the blood of a mammal.
F. Commensalism: One organism benefits, and the other is neither helped nor harmed. For instance,
barnacles attaching to a whale’s skin without harming it.
These interactions shape the structure and dynamics of ecosystems, contributing to biodiversity and the
overall balance of natural systems. The interrelationships are often interconnected in complex webs,
forming the foundation of ecological communities.

General Reproduction
1) Sexual Reproduction:
 Involves the fusion of specialized reproductive cells (gametes) from two parent organisms to
produce offspring.
 Gametes, typically sperm and egg, combine during fertilization, forming a zygote with a
unique combination of genetic material from both parents.
 Results in genetic diversity among offspring due to the shuffling of genetic material during
meiosis.
 Sexual reproduction involves several processes that contribute to the formation of offspring
with genetic diversity. Here are key processes associated with sexual reproduction:
a. Gametogenesis:
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  Description: The formation of specialized reproductive cells called gametes (sperm and
egg).
 Process: Gametes are produced through meiosis, a type of cell division that halves the
chromosome number, resulting in haploid gametes.
b. Fertilization::
 Description The fusion of male and female gametes (sperm and egg) to form a zygote.
 Process: Fertilization typically occurs in a specialized structure, such as the
reproductive organs of plants or the reproductive tract of animals.
c. Syngamy:
 Description: The actual union of the nuclei from the sperm and egg to form a diploid
zygote.
 Process: It represents the culmination of fertilization, bringing together the genetic
material from both parents.
d. Embryogenesis:
 Description: The process of embryo development from the zygote.
 Process: Involves cell divisions, differentiation, and morphogenesis, resulting in the
formation of tissues, organs, and eventually a multicellular organism.
2) Asexual Reproduction:
 Involves the production of offspring without the involvement of gametes or the fusion of
genetic material from two parents.
 The offspring are genetically identical or nearly identical to the single parent organism.
Common methods include budding, binary fission, and vegetative propagation.
 Rapid reproduction and efficient colonization of suitable environments.
 Asexual reproduction involves various processes, each adapted to the specific needs and
characteristics of different organisms. Here are some common processes of asexual
reproduction:
i. Binary Fission:
 Description: Single parent organism divides into two equal parts, each developing into a
new individual.
 Examples: Bacteria, protists, some simple multicellular organisms.
ii. Budding:
 Description: New individuals develop as outgrowths or buds on the parent organism and
eventually detach to live independently.
 Examples: Yeast, hydra (a freshwater organism).
iii. Fragmentation:
 Description: Parent organism breaks into fragments, each capable of growing into a new
individual.
 Examples: Some flatworms, starfish, certain plants like moss.
iv. Vegetative Propagation:
 Description: New individuals develop from vegetative parts like stems, roots, or leaves.
 Examples: Runners in strawberries, tubers in potatoes, plant cuttings.
v. Parthenogenesis:
 Description: Development of an embryo from an unfertilized egg, often in the absence of male
gametes.
 Examples: Some insects, reptiles, and certain species of fish.