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8th Grade Chapter 4: Interactions of Life Notes
Section 1: Living Earth
1. Biosphere is the part of Earth that supports life.
2. The biosphere has 3 parts: the top portion of Earth’s crust, all the waters that cover Earth’s
surface, and the atmosphere that surrounds Earth.
3. The biosphere is made up of different environment that are home to different kinds of
organisms.
4. Ecosystem consists of all the organisms living in an area and the nonliving parts of their
environment.
example – In prairie ecosystem, bison, grass, and birds are living organisms of this
ecosystem. Water, temperature, sunlight, soil, and air are nonliving features of this
ecosystem
5. Ecology is the study of interactions that occur among organisms and their environment.
6. Interaction – influence, effect, response, reaction, etc.
7. A population is made up of all the (same) organisms in an ecosystem that belong to the
same species.
8. A community is all the (different) populations in an ecosystem.
9. Habitat is the place in which an organism lives.
10. An organism’s habitat must provide the kinds of food, shelter, temperature, and moisture the
organism needs to survive. example – trees are the woodpecker’s habitat
Section 2: Populations
11. Competition is when two or more organisms seek the same resource at the same time.
12. Competition for food, living space, or other resources can limit the population’s size.
13. Competition is usually most intense between members of the same species.
14. Population size indicates whether a population is healthy and growing.
15. Population density is the size of a population that occupies a specific area.
16. There are many things that affect population size like: limiting factors, carrying capacity,
biotic potential, birth and death rates, movement of organisms in or out of an area.
17. Limiting factor is any living or nonliving feature that restricts the number of individuals in a
population.
18. Carrying capacity is the largest number of individuals of one species that an ecosystem can
support.
19. Biotic potential is the highest rate of reproduction under ideal conditions.
20. Exponential growth occurs when a population becomes large and grows faster.
8th Grade Chapter 4: Interactions of Life Notes
Section 3: Interactions Within Communities
21. Sun is the source of energy that fuels most life on Earth.
22. Producers are organisms that use an outside energy source to make energy-rich molecules.
23. Most producers use the Sun and contain chlorophyll, a chemical required for photosynthesis.
24. Photosynthesis is the process by which organisms use sunlight to convert gases into sugar
compounds.
25. Some producers, found near volcanic vents on the ocean floor, use chemicals that contain
carbon (like methane) as a source of energy in chemosynthesis.
26. Consumers are organisms that cannot make their own energy-rich molecules; they obtain
energy by eating other organisms.
27. Herbivores, Carnivore, Omnivores, and Decomposers are all consumers.
28. Herbivores, such as deer and rabbits, eat plants.
29. Carnivores, such as frogs and lions, eat animals
30. Omnivores, such as pigs and humans, eat both plants and animals.
31. Decomposers, such as earthworms and bacteria, eat dead organisms.
32. Food chain is a model that shows the feeding relationship among organisms in an
ecosystem.
33. Symbiosis is any close relationship between species.
34. Mutualism is a symbiotic relationship in which both species benefit.
35. Commensalism is a symbiotic relationship in which one organism benefits and the other is
not affected.
36. Parasitism is a symbiotic relationship in which one organism benefits and the other is
harmed.
37. Niche is an organism’s role in its environment, including its habitat and food, and how it
avoids danger, finds a mate and cares for its young.
38. Predator is a consumer that captures and eats other consumers
39. Prey is the organism that is captured by the predator.
40. Predators limit the size of prey populations, increasing the number of different species that
can live in an ecosystem.
41. Cooperative actions improve a species’ survival.
Example: one deer warns others of predators in the area.
Example: individual ants perform different tasks required for the survival of all.