Population Ecology Chapter 4

GPS SB4 Students will assess the dependence of all organisms on one another and the flow of energy and matter within their ecosystems. d. Assess and explain human activities that influence and modify the environment such as global warming, population growth, pesticide use, and water and power consumption.

 A biological community is a group of interacting populations that occupy the same area at the same time. A desert oasis

Organisms within a community adapt to the conditions in which they live. These conditions are often abiotic factors Communities are often stable but may evolve and change over time.

Keeps a population in check. Doesn’t allow unlimited growth. Limiting factors include: Food, water, shelter/ habitat, mates Organism compete for these limited resources

Population Dynamics Populations of species are described by density, spatial distribution, and growth rate

Population Characteristics Population Density The number of individuals per unit area Spatial Distribution The pattern of spacing of a population

Population Ranges Populations can not live in all environments Abiotic conditions effect the range of environments in which a population can live A species might not be able to expand its population range because it cannot survive the abiotic conditions found in the expanded region.

Population Limiting Factors There are two categories of limiting factors 1.density-independent factors Any factor in the environment that does not depend on the number of members in a population per unit area 2.density-dependent factors Any factor in the environment that depends on the number of members in a population per unit area

Disease Temperature Competition Parasites Storms Food Habitat disruption Drought

Environmental limits to population growth Density-dependent factors disease, competition, parasites, and food Density-independent factors temperature, storms, floods, drought, habitat disruption

An upper limit and lower limit that define the conditions in which an organism can survive The ability of any organism to survive when subjected to abiotic factors or biotic factors is called tolerance.

Population Growth Rates

Exponential growth As the population gets large it also grows faster Reasons this occurs: 1. Initial increase is slow because few breeding individuals 2. As individuals mature, reproducing individuals increases. Time Population size

Exponential growth is not realistic Populations tend to grow until some environmental condition stops growth Time Population size This is called Logistic Population Growth!!

Carrying capacity and Limiting factors Keeps a population in check. Doesn’t allow unlimited growth. Limiting factors include: Food, water, shelter/ habitat, mates Organism compete for these limited resources

Reproductive patterns Species of organisms vary in: the number of births per reproduction cycle the age that reproduction begins, the life span of the organism

What causes a population to grow Number of births is greater than the number of deaths Immigration exceeds Emigration.

What causes a population’s numbers to decrease? Number of births is less than the number of deaths Emigration exceeds immigration.

2 Reproductive Patterns K-strategist –Little environmental change –Generally large organisms –Long life spans –Few offspring with extended parent care R-strategist –Fluctuating abiotic factor occur –Generally small organisms –Short life span –Many offspring

Elephants Bacteria Mice Humans Cows Termites Lions Rabbits

Demography- the study of human population growth characteristics. Age structure-proportions of a population that are at different age levels.

Predator prey relationships