Presentation on theme: "KEY CONCEPT Organisms interact as individuals and as populations."— Presentation transcript:
1KEY CONCEPT Organisms interact as individuals and as populations.
2Competition and predation are two important ways in which organisms interact. Competition occurs when two organisms fight for the same limited resource.Intraspecific competitionInterspecific competition
3Predation occurs when one organism captures and eats another.
4There are three major types of symbiotic relationships. Mutualism: both organisms benefit
5There are three major types of symbiotic relationships. Commensalism: one organism benefits, the other is unharmedHuman Our eyelashes are home to tiny mitesthat 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 folliclesof eyelashes. Magnified here 225 times, these creatures measure 0.4 mm in length and can be seen only with a microscope.+Organism benefitsØOrganism is not affectedCommensalism
6There are three major types of symbiotic relationships. Parasitism: one organism benefits, the other is harmedOrganism benefits_Organism is not affectedHornworm caterpillarThe host hornworm will eventually die as its organs are consumedby wasp larvae.Braconid waspBraconid larvae feed on their host and release themselves shortly before reachingthe pupae stage of development.Parasitism+
7There are three major types of symbiotic relationships. Parasitism meet their needs as ectoparasites (such as leeches) and endopaasites (such as hookworms)
8KEY CONCEPT Each population has a density, a dispersion, and a reproductive strategy.
9Population 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.
10Population dispersion refers to how a population is spread in an area. Geographic dispersion of a population shows how individuals in a population are spaced.Population dispersion refers to how a population is spread in an area.ClumpeddispersionUniformRandom
14Survivorship 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.
15Survivorship curves can be type I, II or III. Type I—low level of infant mortality and an older populationcommon to large mammals and humansType II—survivorship rate is equal at all stages of lifecommon to birds and reptilesType III—very high birth rate, very high infant mortalitycommon to invertebrates and plants
16KEY CONCEPT Populations grow in predictable patterns.
17Changes in a population’s 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.immigrationbirthsemigrationdeaths
18Population growth is based on available resources. Exponential growth is a rapid population increase due to an abundance of resources.
19Logistic growth is due to a population facing limited resources.
20Carrying 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.
21Ecological 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.
22Density-dependent limiting factors are affected by the number of individuals in a given area. predationcompetitionparasitism and disease
23Density-independent limiting factors limit a population’s growth regardless of the density. unusual weathernatural disastershuman activities