BIO 245 | ECOLOGY

CHAPTER 1: INTRODUCTION
4 Laws of Ecology Biotic Components
1. Everything is connected to everything else. - Refer to all living components in an ecosystem.
2. Everything must go somewhere.
3. Nature knows best. Categorized into:
4. There is no such thing as free lunch. • Producers
- Barry Commoner - Include all autotrophs such as plants.
→ Called autotrophs as they can produce food
through the process of photosynthesis.
Ecology - All other organisms higher up in the food chain rely
• Comes from the Greek word oikos which means on producers for food.
“household” and logos which means “study of”.
• Consumers or heterotrophs
• The study of the relations of organisms to one another
- Organisms that depend on other organisms for
and to their physical environment. food.
- Further classified into:
Interdependence o Primary consumers – always herbivores as
• The survival of species is dependent on other living they rely on producers for food.
organisms and non-living components. o Secondary consumers – depend on primary
consumers for energy, can either be carnivores
or omnivores.
Earth o Tertiary consumers – organisms that depend
• Biosphere on secondary consumers for food, can also be
• Planet that meets the conditions to support life. carnivores or omnivores.
• Right light, temperature, and presence of water. o Quaternary consumers – present in some
food chains, prey on tertiary consumers for
Direct Benefits Indirect Benefits energy, usually at the top of a food chain as
• Food • Water and air purification they have no natural predators.
• Water • Cycling of nutrients • Decomposers
• Air • Climate control - Includes saprophytes such as fungi and bacteria.
• Clothing materials • Soil formation - Directly thrive on the dead and decaying organic
• Lumber • Renewal and matter.
decomposition of wastes - Essential for the ecosystem as they help in
recycling nutrients to be reused by plants.

Ecosystem Functional Units of an Ecosystem

• All organisms and non-living environment found in a
particular place. • Productivity – refers to the rate of biomass
• Interact with each other for survival. production.
• Defined as a community of lifeforms in concurrence • Energy flow – sequential process through which
with non-living components, interacting with each energy flows from one trophic level to another. The
other. energy captured from the Sun flows from producers to
consumers and then to decomposers and finally back
to the environment.
Species • Decomposition – process of breakdown of dead
- A group of similar individuals or organisms. organic material. The top-soil is the major site for
decomposition.
Population • Nutrient cycling – in an ecosystem nutrients are
- Consists of individuals of a particular species, in a consumed and recycled back in various forms for the
specific region at a certain time. utilization by various organisms.

Community
- Consists of a group of different species that are
included in biotic interactions (directly or indirectly)
BIO 245 | ECOLOGY
CHAPTER 1: INTRODUCTION
Important Ecological Concepts Habitat
• Food Chain - sequence that shows how energy and - The natural home or environment of an animal,
nutrients flow from one organism to another in an plant, or any other organism.
ecosystem. It starts with a producer (like a plant) and
moves through various consumers (like herbivores and Niche
predators) to decomposers - Unique and specific role an organism plays in its
ecosystem.
- Describing how it responds to the location of
resources, rivals, and predators

Difference between Habitat and

Niche
Habitat Niche
Temperature, rainfall, A movement of energy
and other abiotic from one organism to
• Ecological Pyramids - graphical representations elements all have an another across an
showing the relationship between different levels of a impact on habitat. ecosystem is included in
food chain. They can show the number of organisms, the niche.
biomass, or energy at each level (producers at the Changes For a longer period, Seasons, for example,
base and top predators at the peak). an animal’s habitat can cause living beings
remains the same. to change their niche in
a short period.
Nature It is a physical place. It is a role performed by
organisms.
Specificity Not species-specific Species-specific
Examples Deserts, oceans, Only a section of the
forests, rivers, habitat, the niche, can
mountains, etc. provide safety for living
beings.
Influence A species’ niche may Niche is a habitat
be influenced by its solution that has little
habitat. impact on species’
environments.
• Food Web - a complex network of interconnected
food chains in an ecosystem. It shows how different
species are linked by feeding relationships, highlighting Laws of Thermodynamics
the diversity and stability of an ecosystem.
Four Laws of Thermodynamics
Zeroth law “If two bodies A and B are in thermal
equilibrium with third body C, then body
A and B are also in thermal equilibrium
with each other.”
First law “The net change in total energy of a
system (∆E) is equal to the heat added
to the system (Q) minus work done by
the system (W).”
Second law “In all the spontaneous processes, the
entropy of the universe increases.”
Third law “The value of entropy of a completely
pure crystalline substance is zero at
absolute zero temperature.”
BIO 245 | ECOLOGY
CHAPTER 1: INTRODUCTION
First Law of Thermodynamics
• States that energy cannot be destroyed nor created. It
can only be changed from one form to another.
• “Conservation of energy principle”
• Ingestion = Production + Respiration + Defecation +
Excretion

Optimal Foraging Theory

• A behavioral ecology model that helps predict how an
animal behaves when searching for food. Although
obtaining food provides the animal with energy,
searching for and capturing the food require both
energy and time. To maximize fitness, an animal
adopts a foraging strategy that provides the most Scientific Method
benefit (energy) for the lowest cost, maximizing the net - Series of steps to collect information or solve
energy gained. OFT helps predict the best strategy that problems.
an animal can use to achieve this goal. 1.) Observation
2.) Hypothesis
A study by Tinbergen on Foraging Decision of 3.) Experimentation
Starlings Sturnus vulgaris 4.) Data Analysis
5.) Conclusion
• They feed on Jacket larva
• They make trips to get food
• Question: how many should they get each trip?
• Constraint: they can’t get more larva than their
optimal range because their mouth capacity cannot
cope with it.

Second Law of Thermodynamics

• States that high quality energy is degraded to low
quality energy when it is transformed from one form to
another (due to loss of energy to the surroundings as
heat during the transformation).

Entropy
- It is the tendency of a system to go towards
disorder.

Open system
- A living organism has an open system because of
receiving inputs (O2, food, water) from the
environment, carries out processes, and releases
outputs (heat, CO2, wastes)

Desk Entropy
- A spatiodynamic quantity that measures a
workspace’s degree of disorder, and the inability to
find anything when you really need it.
- Any spontaneous activity, whether productive or
unproductive, disperses matter and increases
overall desk entropy.
- Efforts to reverse desk entropy are temporary, and
inevitably decrease over time.