Page 12 - Science Course 3 (Book 1)

Mo1-L1a: What are Ecosystems?

The community living in this vacant lot includes Key Concept
populations of dandelions, grasses, ants, spiders,
and pigeons. What are Ecosystems?

In what ways can populations change?

Population density is the size of a population
compared to the amount of space available.

When population density is high, organisms live
closer together and might not be able to obtain all
the resources needed for life.

Diseases spread more easily when organisms live SUMMARY
closer together.
What are Ecosystems?

Many organisms often share the same
habitat.

Population density can affect the health of a
population.

Production of offspring increases the size of a
population. The death of individuals reduces
population size.

If births outnumber deaths, the population grows.

4