Biology Unit 7 study games — Ecology and Ecosystems.
This unit covers food webs, energy flow, biomes and population dynamics — essential concepts for Biology. Use our interactive study games to test your understanding, or review questions in traditional format below.
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This unit covers food webs, energy flow, biomes and population dynamics — essential concepts for Biology. Use our interactive study games to test your understanding, or review questions in traditional format below.
Key Concepts Breakdown
1 Food Webs
A food web shows the feeding relationships between organisms in an ecosystem, with arrows pointing from prey to predator (showing energy flow). Students must understand trophic levels, the roles of producers, consumers, and decomposers, and how removing one species affects the rest of the web.
Key Points
- Producers (plants/algae) are always at the base; they make their own food via photosynthesis
- Arrows in a food web point in the direction energy flows (from eaten to eater)
- Removing a keystone species can cause a trophic cascade, destabilizing the entire web
- Decomposers (fungi, bacteria) recycle nutrients but are often not shown in simplified food webs
In a meadow food web: grass → grasshopper → frog → snake → hawk. If frogs are removed by disease, predict what happens to grasshopper and snake populations.
With frogs gone, grasshoppers have no predator, so their population increases. Snakes lose their main prey source, so their population decreases. This is a trophic cascade — a change at one level ripples up and down the web.
2 Energy Flow
Energy enters ecosystems through photosynthesis and flows through trophic levels, but only about 10% is transferred from one level to the next — the rest is lost as heat. Students must be able to apply the 10% rule and explain why food chains rarely exceed 4-5 levels.
Key Points
- Only ~10% of energy at one trophic level is available to the next level
- Energy lost between levels is released as metabolic heat (cellular respiration, movement, body heat)
- Ecological pyramids (energy, biomass, numbers) are almost always wider at the base
- Eating lower on the food chain is more energy-efficient (relevant to human diets)
A field contains 10,000 kcal of energy stored in grass. How much energy is available to primary consumers? To secondary consumers?
Apply the 10% rule at each step: primary consumers receive 10% of 10,000 kcal = 1,000 kcal. Secondary consumers receive 10% of 1,000 kcal = 100 kcal. This shows why large predators are rare — very little original energy reaches the top of the chain.
3 Biomes
Biomes are large-scale ecosystems defined primarily by climate (temperature and precipitation) and characterized by distinct plant and animal communities. Students must match biome types to their key characteristics and understand that latitude and altitude both affect biome distribution.
Key Points
- The two main climate factors determining biome type are annual temperature and annual precipitation
- Tropical rainforests have high biodiversity and year-round warmth and rain; tundra has low biodiversity, permafrost, and minimal precipitation
- Moving from equator to poles mirrors moving from base to top of a mountain (biome succession)
- Terrestrial biomes in order of increasing precipitation: desert → grassland → shrubland → temperate forest → tropical rainforest
A biome has an average temperature of 25°C year-round and receives over 200 cm of rain annually. Identify the biome and name two expected adaptations of organisms living there.
High temperature and very high precipitation together identify this as a tropical rainforest. Expected adaptations include broad, waxy leaves to shed heavy rainfall and buttress roots to support tall trees in shallow rainforest soil. These adaptations directly reflect the biome's defining climate conditions.
4 Population Dynamics
Population dynamics describes how and why population sizes change over time, driven by birth rate, death rate, immigration, and emigration. Students must understand exponential vs. logistic growth, carrying capacity (K), and the factors that limit population size.
Key Points
- Exponential growth (J-curve) occurs when resources are unlimited; logistic growth (S-curve) occurs as population approaches carrying capacity (K)
- Carrying capacity is the maximum population size an environment can sustain long-term
- Density-dependent limiting factors (predation, disease, competition) intensify as population grows; density-independent factors (natural disasters, weather) act regardless of population size
- Population size = (Births + Immigration) − (Deaths + Emigration)
A deer population in a forest grows rapidly after wolves are removed. It overshoots K, then crashes. Sketch the shape of this growth curve and identify what type of growth occurred at each phase.
Initially, with no predators and abundant food, growth is exponential (J-curve shape). As deer exceed K, food becomes scarce — a density-dependent factor — and the population crashes below K. The result is an overshoot-and-crash pattern, which is a variation of logistic growth where the population temporarily exceeds its carrying capacity before declining.
Questions, answered.
What is Ecology and Ecosystems?
Ecology and Ecosystems is Unit 7 of Biology, covering food webs, energy flow, biomes and population dynamics.
How to study for Biology Unit 7?
Start with the Quick Summary above, review the Key Concepts, then test yourself with our interactive study games. Aim for 80%+ accuracy before moving on.
How many questions are in this unit?
This unit has 28+ review questions across 5 different game modes.