Ecosystem Basics
Is sunlight a biotic or abiotic factor?
Abiotic
What is the main source of energy for most ecosystems?
Sunlight
What is ecological succession?
The gradual change in a biological community over time.
What does the vertical axis usually show on a population growth graph?
Population size.
What is biodiversity?
The variety of life.
What is the difference between a population and a community?
A population includes one species. A community includes different populations living together.
What process allows producers to store sunlight as chemical energy?
Photosynthesis
Which type of succession begins on bare rock without soil?
Primary succession.
Which type of population growth produces a J-shaped curve?
Exponential growth.
What are the three types of biodiversity?
Genetic diversity, species diversity, and ecosystem diversity.
What ecological role do fungi and bacteria perform when they break down dead organisms?
Decomposers
Put these organisms in order of energy transfer: fox, grass, rabbit.
Grass → rabbit → fox.
Why does secondary succession usually happen faster than primary succession?
Soil remains, and seeds, roots, or microbes may also remain.
What is carrying capacity?
The population size an environment can support over time with its available resources.
Differences in inherited traits among members of the same species represent which type of biodiversity?
Genetic diversity.
How can removing trees along a stream affect water temperature and erosion?
Water temperature can increase because there is less shade. Erosion can increase because fewer roots hold soil in place.
Why can an ecosystem usually support fewer organisms at higher trophic levels?
Less energy is available at each higher level because organisms use energy and release some as heat.
Does ecosystem equilibrium mean that nothing changes? Explain.
No. Populations and interactions can change while the ecosystem maintains an overall balance.
A population grows quickly and then levels off around 500 individuals. What type of growth does this show, and what is the approximate carrying capacity?
Logistic growth, with a carrying capacity of about 500 individuals.
How can genetic variation help a population survive a new disease?
Some individuals may have inherited traits that help them resist the disease, survive, and reproduce.
Explain how a decrease in bees could eventually cause a decrease in hawks.
Fewer bees can reduce pollination and plant reproduction. Fewer plants support fewer plant-eating animals, leaving less prey for hawks.
Explain the difference between energy flow and matter cycling in an ecosystem.
Energy enters, moves through organisms, and eventually leaves as heat. Matter moves through organisms and the environment and is reused.
A drought ends, but drought-resistant plants now dominate the area. Did the ecosystem necessarily return to its original equilibrium? Explain.
No. Different plants now dominate, which can change competition, resource use, and feeding relationships.
A drought reduces available food and water. Explain how this could affect carrying capacity and a population that exceeds it.
Carrying capacity may decrease. A population above that capacity may decline as competition increases and survival or reproduction decreases.
Explain how habitat loss can reduce biodiversity and affect ecosystem functioning.
Habitat loss removes resources and living space, causing populations to decline. Losing species can disrupt food webs and processes such as pollination and nutrient cycling.