Download Chapter 9 Study Guide

7th Grade Science-Chapter 9 Study Guide
LESSON 9.1
*Populations can change in size when new members join the population or when members leave the
population.
The number of births per 1,000 individuals for a given time period is called birth rate.
The number of deaths per 1,000 individuals for a given time period is called death rate.
If birth rate is higher than death rate, population size increases.
If death rate is higher than birth rate, population size decreases.
Moving into a population is called immigration.
Leaving a population is called emigration.
The number of individuals in an area of a specific size is called population density.
Population density = # of individuals ÷ unit area
Ex: The population density of the area to the right = 1 individual per square meter
Know (memorize) the formula for population density, and be able to use it to
calculate the population density in an example.
XX
3 meters
X
X X X X
X
X
*Some limiting factors for populations are weather conditions, space, food, and water.
An environmental factor that causes a population to stop growing or
decrease in size is called a limiting factor.
The largest population that an area can support is called its carrying capacity.
See graph below for an example of carrying capacity.
carrying capacity
Population
(# of individuals)
----------------------------------------
Time (years)
LESSON 9.2
*Every organism has a variety of adaptations that are suited to its specific environment and help it
survive.
A behavior that helps an organism to survive and reproduce is called a behavioral adaptation.
A structure that helps an organism to survive and reproduce is called a structural adaptation.
Be able to give examples or classify examples as either behavioral or structural adaptations.
3 meters
*Some variations may help individuals survive better in their environment. When members of a species
survive, the population survives.
The process by which individuals with variations most suited to their environments survive and are most
likely to reproduce is called natural selection.
The process of natural selection affects populations over time.
LESSON 9.3
*Two types of succession are primary succession and secondary succession.
The series of predictable changes in a community over time is called succession.
The series of changes that occurs in an area where no soil or no organisms (living things) exist is called
primary succession. Volcanic eruptions can lead to primary succession.
The first species to populate an area is called pioneer species. These species are often carried to areas
by wind or water.
The series of changes that occurs in an area where the ecosystem has been disturbed, but where soil
and organisms still exist is called secondary succession. Fires, hurricanes, and tornados can often lead to
secondary succession.
*Organisms that survive a changing ecosystem have adaptations that help them survive in the new
conditions. Behavioral adaptations are behaviors or actions of an organism that helps it adapt.
Structural adaptations are physical characteristics or structures an organism has that help it adapt.
Be able to identify or give examples of behavioral and structural adaptations.
LESSON 9.4
*The resources that humans obtain from ecosystems include both abiotic and biotic resources.
Anything in an ecosystem that you need to live is called a resource.
Abiotic resources used by humans: water, sunlight, oxygen, and minerals.
Biotic resources used by humans: food, materials to build shelter, and materials that compose fuels.
*Human activities may affect the balance in an ecosystem and thereby change the ecosystem.
Examples include: introducing non-native species and overuse of resources.
*Some technologies used in energy production, agriculture, human habitation, and transportation
impact the environment. Be able to give some specific examples of the technologies used in these areas
that impact the environment.
The process in which certain gases trap the sun’s energy in Earth’s atmosphere as heat is called the
greenhouse effect.
LESSON 9.5
The number of different species in an area is called biodiversity.
*Biodiversity has both economic value and ecological value within an ecosystem.
Economic value-Ex: tourism (African Safari), plants used for medicines
A species that influences the survival of many other species in an ecosystem is called a keystone species.
*Factors that affect biodiversity in an ecosystem include climate, are, niche diversity, genetic diversity,
and extinction.
Climate (Tropical areas are most diverse.)
Area (Large areas usually are more diverse.)
Niche Diversity (If a species has a variety of ways to survive, it will likely thrive.)
Genetic diversity (Populations with genetic diversity are usually thrive.)
Extinction of species (Species that go extinct decrease biodiversity.)
The disappearance of all members of a species form Earth is called extinction.
Species in danger of becoming extinct are called endangered species.
Species that could become endangered in the near future are called threatened species.
*Biodiversity can be negatively or positively affected by the actions of humans.
Damaging effects humans have on biodiversity:
-habitat destruction –the loss of a natural habitat; the major cause of extinction
-habitat fragmentation-breaking larger habitats into smaller, isolated pieces, or fragments
-poaching-illegally killing or removing wildlife from their habitats
-introducing exotic species into an ecosystem (they will sometimes out-compete native species)
Protecting effects humans have on biodiveristy: captive breeding-the mating of animals in zoos or
wildlife preserves, in order to preserve an endangered species.
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