Ecosystems Basics
What is an ecosystem?
An ecosystem is a system where living things interact with non-living things, such as water, sunlight, soil, and air, in a specific place.
What is a biome?
A biome is a large region of the Earth defined by similar climate conditions, vegetation, and animal life, such as deserts, grasslands, tundra, and rainforests.
What is a food web?
A food web is a network of interconnected food chains that shows how energy moves between producers, consumers, and decomposers in an ecosystem.
Which climate factor explains why areas near the equator are generally warmer than areas near the poles?
Latitude, because places near the equator receive more direct sunlight year-round.
Explain how living and non-living factors work together in an ecosystem.
Living organisms depend on non-living factors such as sunlight, water, soil, and temperature for survival. For example, plants need sunlight and water to grow, and animals depend on plants for food.
Explain the role of decomposers in an ecosystem.
Decomposers break down dead plants and animals into nutrients that return to the soil and support plant growth.
Explain the difference between a biome and an ecosystem.
A biome is a large region defined by its climate and typical plants and animals, such as a desert or rainforest, while an ecosystem is a smaller system within a biome where living and non-living things interact, such as a pond ecosystem within a forest biome.
Explain why food webs are more realistic than food chains in showing how ecosystems function.
Food webs are more realistic because most organisms have multiple food sources and predators. For example, several animals may eat grass, and predators may hunt more than one prey species.
Two cities are located at the same latitude, but one has milder temperatures year-round.
Which climate factor most likely explains this difference?
Distance from the sea, because large bodies of water moderate temperature.
A climate graph shows warm temperatures year-round and high precipitation in every month.
Identify the most likely biome and explain how the graph supports your conclusion.
The biome is a rainforest. Constant warmth supports continuous plant growth, and year-round precipitation provides enough water for dense vegetation.
Explain how removing one group of organisms could disrupt an ecosystem.
Removing one group can reduce food sources, interrupt nutrient cycling, and cause population changes throughout the ecosystem.
Explain why grasslands are dominated by grasses instead of large forests.
Grasslands have seasonal rainfall and long dry periods that limit tree growth, while grasses survive because they require less water and can regrow quickly after dry seasons.
Explain the difference between an apex predator and a tertiary consumer.
A tertiary consumer feeds on secondary consumers, while an apex predator is a top-level consumer that is not preyed upon by other animals. Some apex predators are tertiary consumers, but not all tertiary consumers are apex predators.
The hawk feeds on a secondary consumer and is not preyed upon by other animals, so it is both a tertiary consumer and an apex predator.
The fox is a tertiary consumer because it eats a secondary consumer, but it is not an apex predator because it can be preyed upon by the eagle.
Explain how altitude can cause a place near the equator to have cooler temperatures than expected.
Higher altitudes have thinner air, which holds less heat, causing temperatures to be cooler even in tropical regions.
A climate graph shows moderate temperatures and seasonal rainfall with a clear wet and dry period.
Identify the biome and explain why this graph does not represent a rainforest.
The biome is a grassland. Rainforests require high rainfall year-round, but the dry season shown on the graph limits continuous tree growth.
Explain the differences between primary, secondary, and tertiary consumers, and give one example of each from an ecosystem.
Primary consumers eat producers, secondary consumers eat primary consumers, and tertiary consumers eat secondary consumers, such as grass → rabbit → snake → hawk.
Compare rainforests and deserts by explaining how precipitation affects the type of vegetation found in each biome.
Rainforests receive high, year-round precipitation, which supports dense vegetation such as tall trees, vines, and layered plant growth. In contrast, deserts receive very little precipitation, so vegetation is sparse and consists mainly of drought-adapted plants like cacti and shrubs that reduce water loss.
Classify each organism as a producer, primary consumer, secondary consumer, or tertiary consumer:
grass → grasshopper → frog → snake
Grass = producer
Grasshopper = primary consumer
Frog = secondary consumer
Snake = tertiary consumer
Why might two locations at the same latitude experience very different precipitation levels?
Differences in distance from the sea or ocean currents can affect moisture availability, causing one location to be wetter while another remains dry even at the same latitude.
Explain how a change in one climate factor could affect both food chains and food webs in an ecosystem.
A change in one climate factor, such as temperature or precipitation, can affect food chains and food webs by first impacting producers. If climate conditions limit plant growth, producers decline, reducing the energy available to primary consumers. As primary consumers decrease, secondary and tertiary consumers also lose food sources, disrupting individual food chains. Because food webs are made up of many connected food chains, these disruptions spread throughout the ecosystem, reducing stability and biodiversity.
Explain why ecosystems can support fewer tertiary consumers than primary or secondary consumers.
At each trophic level, energy is lost as heat and through life processes, so much less energy reaches tertiary consumers. Because they are at a higher trophic level, ecosystems can support fewer tertiary consumers than primary or secondary consumers.
Explain how two climate conditions in the tundra limit plant growth and give one example of a plant adaptation that allows survival.
The tundra’s extremely cold temperatures and permanently frozen soil (permafrost) limit plant growth by preventing deep roots and shortening the growing season. As a result, plants such as mosses and grasses grow low to the ground, which helps them conserve heat and survive strong winds.
In a grassland food web, a drought causes grass populations to decline.
Explain how this change would affect two other organisms in the web.
Herbivores such as antelope would decline due to less food, and predators such as lions would then decrease because fewer prey are available.
Two climate graphs show similar temperatures, but one has year-round rainfall while the other has a long dry season.
Explain how this difference would affect vegetation in each biome.
Year-round rainfall supports dense, layered vegetation like rainforests, while seasonal rainfall limits vegetation to grasses and scattered trees, typical of grasslands.
Explain how removing an apex predator could indirectly affect producers in a food web.
Without apex predators, prey populations—often primary consumers—can increase. Increased grazing reduces producer populations, disrupting the balance of the ecosystem through a trophic cascade.