Populations Unit 3 Lesson 1

Lesson 1 1.Complexity of Nature 2.Population Distribution 3.Factors that Regulate Abundance & Distribution 4.Factors that Influence Population Size 5.Types of Resource Partitioning 6.Predator/Prey Model 7.Density Independent Factors 8.Generalist vs Specialist 9.Reproductive Strategies Unit 3

Nature exists at several levels of complexity Biotic components only Abiotic and biotic Old people can’t eat beans Evolution occurs at this level organism

Population Distribution Random Distribution - No pattern Example: Forests & Coral Reefs Uniform Distribution - Uniform Examples: Plantations & Territorial animals Clumped distribution – Clumped together Examples: Schooling fish, Herding animals, & Flocking birds

Factors that Regulate Abundance & Distribution Population Ecology: The study of factors that cause populations to increase or decrease. Population size: The total number of individuals within a defined area at a given time. Population density: The number of individuals per unit area at a given time. Population distribution: How individuals are distributed with respect to one another. Population sex ratio: The ratio of males to females (China & India are imbalanced) Population age structure: How many individuals fit into particular age categories. Natality - Making new offspring by birth, hatching, germination or cloning Fecundity - Physical ability to reproduce Fertility - Measure of actual number of offspring produced. Mortality – Death rate Factors that Increase/Decrease Populations

Factors that Influence Population Size Review from Unit 2 Density-dependent factors - the size of the population will influence an individual’s probability of survival. Density-dependent factors operate only when the population density reaches a certain level. These factors operate most strongly when a population is large and dense. They do not affect small, scattered populations as greatly. – Examples: Food, water, habitat, competition, disease, parasitism – Competition: When populations become crowded, organisms compete for food, water space, sunlight and other essentials. Competition among members of the same species is a density- dependent limiting factor. Competition - the struggle of individuals to obtain a limiting resource.

Factors that Influence Population Size Competitive exclusion principle Two species competing for the same limiting factor cannot coexist.

Types of Resource Partitioning Temporal: same resource but at different times (wolf/coyote) Spatial: use of different habitats: finches Morphological: difference in body shape or size: ferret/ermine.

Predator/Prey Model Predator/Prey Relationship - This graph represents the population cycles for the snowshoe hare and the Canadian lynx. At one time, scientists believed these curves provided evidence that these predator and prey populations regulated one another. More recent research suggests that the periodic swings in the hare population are caused by a combination of top-down population control — through predation by lynx and other predators — and bottom-up population control, in which changes in the availability of the food supply for hares help to determine their population size, which in turn helps to determine the lynx population size.

Factors that Influence Population Size Review from Unit 2 Density-independent factors - the size of the population has no effect on the individual’s probability of survival. – Examples are any type of a climatic event like hurricane, flood, tornado, volcano eruption, drought

Generalist vs Specialist Generalist – Large/wide niche – Wide range of diet – usually omnivores – Tolerates a wide range of environmental variations – Tolerates environmental changes – Commonly invasive species – Examples: Cockroaches, rats, raccoon Specialist – Small/narrow niche – Limited/unique diet requirements – More likely to suffer from habitat loss and become endangered – Does NOT tolerate environmental changes – Commonly found in stable climax communities – Examples: Koala, giant panda, walrus

Reproductive Strategies K -selected strategists Long life Slower growth Late maturity Fewer large offspring High parental care & protection High investment in individual offspring Adapted to stable environment Later stages of succession Specialists Predators High trophic level Examples: Kangaroos, primates, wolves, whales, elephants r-selected strategists Short life Rapid growth Early maturity Many small offspring Little parental care & protection Little investment in individual offspring Adapted to unstable environment Pioneers, colonizers Generalists Prey Low-trophic level Examples: Rabbits, insects, rodents, invertebrates, parasites, annual plants

End of Unit 3 Lesson 1