Chapter 2 + case study

Absolutely, Pookie! Here’s a full, Chapter 2 ESS breakdown based on the IB ESS SL syllabus — clear, simplified, and exam-focused to help you get that 7. Chapter 2 is called Ecosystems and Ecology and is full of definitions, diagrams, and processes you must know.

🌱 ESS Chapter 2: Ecosystems and Ecology – Breakdown

📌 2.1 Species and Populations

✅ Key Definitions:

• Species: A group of organisms that can interbreed and produce fertile offspring.

• Population: A group of the same species living in the same area at the same time.

• Habitat: The environment where a species lives.

• Niche: The role of an organism in its ecosystem.

• Community: All organisms in an area.

• Ecosystem: A community and its abiotic (non-living) environment.

✅ Concepts:

• Biotic factors: Living parts (e.g., predation, disease).

• Abiotic factors: Non-living parts (e.g., pH, temperature, light).

• Limiting factors: Things that slow population growth (e.g., space, food, disease).

• Carrying capacity: Max number of individuals an area can support.

📌 2.2 Communities and Ecosystems

✅ Terms to Know:

• Producer (autotroph): Makes own food (e.g., plants).

• Consumer (heterotroph): Eats other organisms.

• Decomposer: Breaks down waste/dead matter (e.g., fungi).

• Trophic levels: Feeding levels (producer → primary consumer → secondary…).

✅ Diagrams:

• Food chains: One path of energy.

• Food webs: Many interconnected food chains.

• Pyramid of numbers, biomass, energy:

  • Energy pyramids are always pyramid-shaped (10% energy rule).

📌 2.3 Flows of Energy and Matter

✅ Energy Flow:

• Sun → producer → consumer.

• Energy is lost as heat at each level (2nd law of thermodynamics).

• 10% rule: Only ~10% of energy moves up each trophic level.

✅ Matter Flow (cycles):

• Carbon cycle: Photosynthesis, respiration, combustion, fossil fuels.

• Nitrogen cycle: Nitrogen fixation, nitrification, assimilation, denitrification.

• Know names of bacteria involved.

• Water cycle: Evaporation, condensation, precipitation, transpiration.

📌 2.4 Biomes, Zonation, and Succession

✅ Biomes:

• Large ecosystems (e.g., tundra, desert, rainforest).

• Determined by temperature and precipitation (climate).

• Know how to read a climate graph.

✅ Zonation:

• Spatial patterns in a habitat (e.g., from sea shore to cliff).

• Caused by abiotic factors like salinity or exposure.

✅ Succession:

• Succession: Change in ecosystems over time.

  • Primary: Starts from bare rock.

  • Secondary: After disturbance like fire.

• Climax community: Final stable stage.

• Pioneer species: First colonizers.

📌 2.5 Investigating Ecosystems

✅ Sampling Techniques:

• Quadrats: Count organisms in a square.

• Transects: Line or belt to study distribution.

• Capture–mark–recapture: Used to estimate population size:

  Population size=n1×n2m2\text{Population size} = \frac{n₁ × n₂}{m₂}

  (n₁ = number caught & marked, n₂ = total in second sample, m₂ = marked recaptured)

✅ Abiotic measurements:

• Light, temperature, soil pH, wind speed, salinity, etc.

✅ Simpson’s Diversity Index:

D=N(N−1)∑n(n−1)D = \frac{N(N - 1)}{\sum n(n - 1)}

• N = total number of organisms

• n = number of individuals per species

• Higher D = more diversity

📚 Exam Tips for Chapter 2

• Always define key terms (IB loves definitions!).

• Use real-life examples for biomes and succession.

• Practice drawing & labeling energy pyramids and cycles.

• Apply formulas for Simpson’s Index and population estimates.

• Use past paper Qs on food chains, succession, and sampling methods.

Perfect, Pookie! Here's a super clear case study breakdown for Topic 2 (Ecosystems and Ecology) based on the ones you mentioned and the syllabus focus. This will give you solid examples to use in essays, data responses, and Paper 2 Section B.

🔬 CASE STUDY 1: DDT and Silent Spring

📖 Background:

• DDT (dichlorodiphenyltrichloroethane) is a synthetic pesticide used widely in agriculture and to control malaria.

• Made famous by Rachel Carson’s 1962 book Silent Spring, which exposed its negative environmental impacts.

☠ Key Impacts:

• Bioaccumulation: DDT builds up in the fat tissues of organisms.

• Biomagnification: Increases in concentration up the food chain — top predators most affected.

• Birds of prey: Like eagles and falcons had thin eggshells → population decline.

• Health risks: DDT is possibly linked to cancer and developmental issues in humans.

🌍 Relevance to ESS:

• Energy & matter flows: Bioaccumulation shows how matter flows through food chains.

• Value systems: Conflict between technocentric (malaria control) and ecocentric (ecosystem harm) views.

• Environmental decision-making: Led to bans (e.g., US banned DDT in 1972).

🌱 CASE STUDY 2: Biomes – Distribution, Climate, Biodiversity

🌍 Key Biomes You Should Know:

📚 Use These for:

• Succession → e.g., primary succession in tundra after glacial retreat.

• Energy flow → e.g., high NPP in rainforests, low in deserts.

• Zonation → e.g., mangrove to inland zonation or alpine zonation.

Of course, Pookie! Here are the two key definitions you need — super short and IB-exam ready:

✅ Bioaccumulation

Definition:
The build-up of a toxic substance in the body of one organism over time.

🧠 Example: DDT accumulating in the fat tissues of fish.

✅ Biomagnification

Definition:
The increase in concentration of a toxic substance as it moves up the food chain.

🧠 Example: DDT levels getting higher from fish → birds that eat the fish.

Let me know if you want a memory trick or diagram to help with these!