Ecology Test 2025-2026 :D

What is the definition of Ecology?

The scientific study of interactions between organisms and their environment (both biotic and abiotic components).

What is the difference between an Ecosystem and a Community?

Community: All the different populations of species in an area.

Ecosystem: The community PLUS the abiotic factors it interacts with.

What is the difference between a Food Chain and a Food Web?

Food Chain: A single, linear pathway of energy flow

Food Web: A complex, interconnected network of many food chains.

What does the 10% Rule for energy flow state?

Only about 10% of the energy from one trophic level is transferred to the next. The rest is used for processes or lost as heat.

What is the 10x Rule for pollutants like DDT?

The concentration of non-biodegradable pollutant increases by about 10 times with each step up the food chain (due to bioaccumulation and biomagnification).

Does energy get recycled in an ecosystem? Do nutrients?

Energy: NO, it flows in one direction (sun → heat)

Nutrients: YES, they are recycled through biogeochemical cycles

What does an Ecological Pyramid represent?

The sharp decrease in energy, biomass, or numbers of organisms from lower to higher trophic levels.

What is a Trophic Level? Name the main levels.

A feeding position in a food chain.

1. Producers

2. Primary Consumers

3. Secondary Consumers

4. Tertiary Consumers

5. Decomposers act at all levels

What is the key difference between Primary and Secondary Succession?

Primary: Starts in an area with no soil (e.g., bare rock)

Secondary: Starts in an area where soil is already present.

What are Pioneer Species and what is a Climax Community?

Pioneer Species: The first organisms to colonize a barren area (e.g., lichens, mosses).

Climax Community: The stable, end-stage community of succession (e.g., mature forest).

Define the three types of Symbiosis and give an example of each.

1. Mutualism (++): Both benefit. (e.g., Bee and flower).

2. Commensalism (+0): One benefits, the other unaffected. (e.g., Barnacles on a whale).

3. Parasitism (+-): One benefits, the other is harmed. (e.g., Tick on a dog).

In a predator-prey graph, how do the population curves relate to each other?

The predator population lags slightly behind the prey population in a cyclical pattern.

What is the role of a Decomposer? Give an example.

To break down dead organic matter and return nutrients to the ecosystem. (e.g., Fungi, Bacteria).

What is the role of Nitrogen-Fixing Bacteria in the Nitrogen Cycle?

They convert atmospheric nitrogen (N₂) into a usable form, ammonia (NH₃), often living in soil or root nodules.

What human activity is the primary cause of the enhanced Greenhouse Effect and Climate Change?

Burning fossil fuels, which increases the concentration of greenhouse gases (like CO₂) in the atmosphere.

What is Ozone Depletion and what primarily causes it?

The thinning of he ozone layer. Caused by CFCs (chlorofluorocarbons), allowing more UV radiation to reach Earth.

What is Acid Rain and what causes it?

Rainfall with a low pH. Caused by sulfur dioxide and nitrogen oxides from burning fossil fuels reacting with water in the atmosphere.

What is Eutrophication and what causes it?

An excess of nutrients (e.g., from fertilizer) in water, causing algal blooms that die, decompose, and deplete oxygen, creating “dead zones.”

What is the difference between Exponential (J-curve) and Logistic (S-curve) growth?

Exponential: Unlimited growth under ideal conditions

Logistic: Growth that slows and stabilizes as it reaches the environment’s Carrying Capacity. 

What is the Carrying Capacity?

The maximum number of individuals an environment can sustainably support. It’s the flat line at the top of an S-curve graph.