Presentation on theme: "14.2 Community Interactions KEY CONCEPT Organisms interact as individuals and as populations."— Presentation transcript:
14.2 Community Interactions KEY CONCEPT Organisms interact as individuals and as populations.
14.2 Community Interactions Competition and predation are two important ways in which organisms interact. Competition occurs when two organisms fight for the same limited resource. –Intraspecific competition –Interspecific competition
14.2 Community Interactions Predation occurs when one organism captures and eats another.
14.2 Community Interactions There are three major types of symbiotic relationships. –Mutualism: both organisms benefit
14.2 Community Interactions –Commensalism: one organism benefits, the other is unharmed Human Our eyelashes are home to tiny mites that feast on oil secretions and dead skin. Without harming us, up to 20 mites may be living in one eyelash follicle. Demodicids Eyelash mites find all they need to survive in the tiny follicles of eyelashes. Magnified here 225 times, these creatures measure 0.4 mm in length and can be seen only with a microscope. + Organism benefits + Ø Ø Organism is not affected Commensalism There are three major types of symbiotic relationships.
14.2 Community Interactions –Parasitism: one organism benefits, the other is harmed There are three major types of symbiotic relationships. Organism benefits 0 _ Organism is not affected Hornworm caterpillar The host hornworm will eventually die as its organs are consumed by wasp larvae. Braconid wasp Braconid larvae feed on their host and release themselves shortly before reaching the pupae stage of development. _ Parasitism + 0
14.2 Community Interactions There are three major types of symbiotic relationships. –Parasitism meet their needs as ectoparasites (such as leeches) and endopaasites (such as hookworms)
14.2 Community Interactions KEY CONCEPT Each population has a density, a dispersion, and a reproductive strategy.
14.2 Community Interactions Population density is the number of individuals that live in a defined area. Population density is a measurement of the number of individuals living in a defined space. Scientists can calculate population density.
14.2 Community Interactions Population dispersion refers to how a population is spread in an area. Geographic dispersion of a population shows how individuals in a population are spaced. Clumped dispersion Uniform dispersion Random dispersion
14.2 Community Interactions There are three types of dispersion. –clumped
14.2 Community Interactions There are three types of dispersion. –uniform
14.2 Community Interactions There are three types of dispersion. –random
14.2 Community Interactions Survivorship curves help to describe the reproductive strategy of a species. A survivorship curve is a diagram showing the number of surviving members over time from a measured set of births.
14.2 Community Interactions Survivorship curves can be type I, II or III. –Type Ilow level of infant mortality and an older population –common to large mammals and humans –Type IIsurvivorship rate is equal at all stages of life –common to birds and reptiles –Type IIIvery high birth rate, very high infant mortality –common to invertebrates and plants
14.2 Community Interactions KEY CONCEPT Populations grow in predictable patterns.
14.2 Community Interactions Changes in a populations size are determined by immigration, births, emigration, and deaths. The size of a population is always changing. Four factors affect the size of a population. –immigration –births –emigration –deaths
14.2 Community Interactions Population growth is based on available resources. Exponential growth is a rapid population increase due to an abundance of resources.
14.2 Community Interactions Logistic growth is due to a population facing limited resources.
14.2 Community Interactions Carrying capacity is the maximum number of individuals in a population that the environment can support. A population crash is a dramatic decline in the size of a population over a short period of time.
14.2 Community Interactions Ecological factors limit population growth. A limiting factor is something that keeps the size of a population down. Density-dependent limiting factors are affected by the number of individuals in a given area.
14.2 Community Interactions Density-dependent limiting factors are affected by the number of individuals in a given area. –parasitism and disease –predation –competition
14.2 Community Interactions Density-independent limiting factors limit a populations growth regardless of the density. –unusual weather –natural disasters –human activities