Download Section 1: chapter 20 Organism-living thing An organism obtains

Section 1: chapter 20
Organism-living thing
An organism obtains food, water, shelter, and other things it needs to live, grow, and reproduce from its
environment.
Habitat- the environment of the organism.
Biotic factors-living part of the habitat.
Abiotic factors- non living part of the habitat: water, sunlight, oxygen, temperature, soil.
Species- is a group of organisms that are physically similar and can mate with each other
Population-all members of one species in an area.
Community-all populations that live together in an area.
Ecosystem-the community of organisms along with the non living surroundings that live in an area.
Determining population size Section 2
Direct observation-to count all of the members
Indirect observation-to observe signs of the organism
Sampling-estimate- approximation of the number of organisms based on assumptions
Mark and recapture studies-capture and mark the animals, two weeks later capture more, count which
ones have marks and which ones do not, use a formula and find the average.
Changes in population size occur when new members join or members leave.
Birth rate is number of births in a certain time.
Death rate is number of deaths in a certain time.
Immigration-moving into an area.
Emigration-leaving a population.
Population density-the number of individuals in an area of a specific size.
Limiting factor-factor that causes a population to decrease.
Carrying capacity-largest population an area can support.
Weather conditions can limit population growth.
Interactions among living things section 3
Natural selection-individuals whose characteristics are best suited for their environment tend to survive
and produce offspring.
Adaptation-behaviors and physical characteristics that allow organisms to live successfully in their
environments.
Niche-the role an organisms plays in its environment.
There are three major types of interactions among organisms:
1. Competition is the struggle between organisms to survive as they attempt to use limited resources.
2. Predation-interaction in which one organism kills and eats another.
Predator-killer
Prey-animal killed
3. Symbiosis-close relationship between two species that benefits at least one of them.
Three types are: mutualism, commensalism, and parasitism
a. Mutualism is when both species benefit.
b. Commensalism is w hen One is helped and the other is neither helped or harmed.
c. Parasitism is when one organism lives in or on another organism and harms it.
Changes in Communities: Section 4
Succession-predictable changes that occur over time.
Primary succession is the series of changes that occur in an area without soil or organisms.
Pioneer species-first species to populate an area.
Secondary succession is the series of changes that occur in an area where the ecosystem has been
disturbed but where soil and organisms still exist.