1. Unit 3 – Ecological Organizations
Ecology – the study of the interactions among living things, and between living things and their surroundings.
6 levels of organization:
organism – individual living thing
population – group of individuals of the same species in an area at a certain time.
community – a group of populations in a certain area.
ecosystem – all the organisms in an area along with non-living factors (climate, water, soil, etc.)
biome – major regional or global community of organisms
biosphere – anywhere on earth where life is found, from high mountains to deep ocean trenches

2. Biotic and Abiotic Factors
Biotic factors – living things such as bacteria, fungus, plants and animals
Abiotic factors – non-living things such as moisture, temperature, wind, sunlight and soil.
Biodiversity – variety of living things in an ecosystem
Keystone Species – species that has an unusually large effect on an ecosystem.

3. Energy in Ecosystems Producers : Consumers:
get their energy from non-living sources (make their own food), sometimes called autotrophs
Get their energy either by photosynthesis (from light) or chemosynthesis (from chemicals)
Consumers:
get their energy by consuming/eating another living thing (dead or alive), sometimes called heterotrophs.

4. Questions 1-2, page 400
What are the five different levels of organization studied by ecologists?
- organism, population, community, ecosystem, biome.
Describe the three general methods used by ecologists to study organisms.
Observation is the act of watching something over time, such a population of birds. Experimentation can occur in the lab or in the field and involves testing a hypothesis. Modeling is a computer-based or math-based method used to predict how changes in one variable may affect another.

5. Questions 3-4, p400
What ecological research methods would you use to study bird migration? Explain your choices.
Observation – band birds and capture them at each end of their migratory route to record their movement. Experimentation – devise an experiment to test the what triggers migration. Modeling – develop a computer model that includes different variables that might predict the time and path of migration.
How might an ecologist use modeling to study fire in a forest ecosystem? What might be some key variables used to create the model?
Sample answer: Ecologists could use models to determine movement of fire, locations where prescribed burns should take place, and areas with the potential for fire outbreaks. Key variables might include forest density, types of trees, plant and animals populations, wind patterns, and weather conditions.

6. Question 5, p400
Ernst Haeckel was greatly influenced by the writings of Charles Darwin. How do the principles of ecology relate to understanding how adaptations occur?
- Species are adapted to their environments. This concept is directly related to the study of ecology, in which the interactions between organisms and the environment are studied. By understanding the interactions within an ecosystem, scientists can develop an understanding of how populations evolve in response to their environments.

7. Questions 1-2, p404
Select an ecosystem that is familiar to you and describe the biotic and abiotic factors that exist there.
- Answers should show that students understand that biotic factors are living things and abiotic are non-living.
How would the removal of a keystone species affect an ecosystem’s biodiversity?
The removal of a keystone species would decrease the ecosystem’s biodiversity.

8. Explain how a change in a an abiotic factor such as sunlight would affect biodiversity.
- Changes in amount of sunlight might affect local temperatures, leading to a change in the numbers and types of species in the ecosystem. New species may move into the area, taking the place of those that cannot survive.
Human are sometimes described as being a keystone species. Does this label fit? Why or Why not?
Keystone species are those that help to establish and maintain a complex web of life. Humans do not fit this label because human activities often decrease, rather than increase biodiversity.

9. What role might an abiotic factor such as temperature play in the evolution of a species?
A long-term temperature change could result in selective pressure that selects for individuals better adapted to the temperature, causing populations to evolve. It could alter the types of food available, again creating selective pressure toward individuals that can take advantage of different food sources.

10. Questions 1-3, page 407
How does the stability of an ecosystem depend on its producers?
Producers bring energy into an ecosystem
What are the two processes used by producers to obtain energy?
Photosynthesis and chemosynthesis
Few producers live deep below a lake’s surface. Suggest an explanation for this pattern.
- sunlight cannot penetrate the water to a great depth, so photosynthesizing organisms are more common near the surface.

11. Could producers survive without consumers? Explain why or why not?
- Producers do not require consumers to fill material needs as a food source. So in that sense, producers do not need consumers to survive.
How might chemosynthetic organisms help scientists to understand how life developed on Earth?
- Chemosynthetic organisms live in environments that may be similar to those that existed on Earth billions of years ago, when life was beginning to develop. Studying these organisms enables scientists to infer how different life forms may have evolved as Earth changed.

12. Questions 1-2, p411
Why are food chains especially useful for describing the relationships of specialists?
Specialists have specific diets that include only one type of organism, which produces a simple food chain.
What happens to energy as it flows through a food web?
Some energy is stored in the organism (10%), but much energy is dissipated into the environment (90%).

13. Only a small percentage of all consumers are specialists
Only a small percentage of all consumers are specialists. What danger does a specialist faces that a generalist does not?
If a specialist’s food source becomes scarce or disappears, the population may die out. A generalist facing the loss of one of its food sources can shift to a different food source.
How might the stability of an ecosystem be affected if all the decomposers were suddenly removed?
The stability of the ecosystem would be negatively affected because without decomposers, vital nutrients would not be returned into the environment.

14. Question 5
How might an oil spill in the ocean affect an aquatic food web? What might happen to the food web on land located near the spill? Explain your answers.
- The entire food web would be affected by the oil spill. Oily water may kill off phytoplankton. The loss of smaller fish would affect larger fish, which in turn affect tertiary consumers. Plants and animals that live along the coast would also be affected as the oil seeped onto the shore. The overall effect would be a decline in the availability of food sources both within and outside the ocean.

15. Questions 1-3, p416
How does the hydrological cycle move water through the environment?
Precipitation falls to Earth, and transpiration and evaporation transfer water back into the atmosphere as water vapour.
What are four elements that cycle through ecosystems, and why are they important?
- oxygen, carbon, nitrogen and phosphorus; they are all necessary for life on Earth.
Why might farmers plant legumes such as peas to improve the nitrogen levels in their soil?
- Legumes have root nodules, which contain nitrogen-fixing bacteria. Increased levels increase the fertility of the soil.

16. Explain the importance of decomposers to the overall biogeochemical cycle.
Decomposers break down organisms and release various elements, including nitrogen and phosphorus, which other organisms can then use.
How might Earth’s biogeochemical cycles help scientists to understand the early history of life on Earth?
- Studies of the biogeochemical cycles and how they interact may help scientists reconstruct the sequence of events that led to changes at Earth’s surface that would enable different types of organisms to evolve.

17. Questions 1-3, p419
How does an energy pyramid help to describe energy flow in a food web?
An energy pyramid shows the relative contribution to energy flow made by each trophic level in an ecosystem.
What is the difference between a biomass pyramid and a pyramid of numbers?
A biomass pyramid compares the mass of organisms that make up each trophic level in an ecosystem; a pyramid of numbers compares the number of individual organisms that make up each trophic level.

18. How would you draw a pyramid of numbers for a dog with fleas
How would you draw a pyramid of numbers for a dog with fleas? What shape would it take?
- The bottom level would be the dog, and the fleas would be the top level. This would be an inverted pyramid because there are many fleas to just one dog.
If each level in a food chain typically loses 90 percent of the energy it takes in, and the producer level uses 1000 kcal of energy, how much energy is left after the third trophic level?
The first trophic level uses 1000 kcal; the second trophic level uses 100 kcal; the third trophic level uses 10 kcal, leaving 1 kcal

19. Question 5, p419
Why is a herbivorous diet more energy efficient than a carnivorous diet? Explain your answer.
a herbivorous diet is more energy efficient because it is the closest trophic level to producers, meaning there is more available energy to use.