Interactions in Ecology Chapter 14 Habitat and Niche

Interactions in Ecology Chapter 14 Habitat and Niche Community Interactions Population Density Population Growth Ecological Succession

KEY CONCEPT Every organism has a habitat and a niche.

A habitat differs from a niche. • A habitat is all aspects of the area in which an organism lives. – biotic factors – abiotic factors • An ecological niche includes all of the factors that a species needs to survive, stay healthy, and reproduce. – food – abiotic conditions – behavior

Resource availability gives structure to a community. • Species can share habitats and resources. • Competition occurs when two species use resources in the same way. • Competitive exclusion keeps two species from occupying the same niche.

• Competitive exclusion has different outcomes. – One species is better suited to the niche and the other will either be pushed out or become extinct. – The niche will be divided. – The two species will further diverge.

• Ecological equivalents are species that occupy similar niches but live in different geographical regions. Madagascar South America

KEY CONCEPT Organisms interact as individuals and as populations.

• Competition and predation are two important ways in Competition occursorganisms when two organisms fight for the which interact. same limited resource. – Intraspecific competition – Interspecific competition

• Predation occurs when one organism captures and eats another.

• There are three major types of symbiotic relationships. – Mutualism: both organisms benefit

• There are three major types of symbiotic relationships. – Commensalism: one organism benefits, the other is unharmed Ø 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. Commensalism Ø Organism is not affected + + Organism benefits 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.

• There are three major types of symbiotic relationships. – Parasitism: one organism benefits, the other is harmed 0 Parasitism _ + Hornworm caterpillar The host hornworm will eventually die as its organs are consumed by wasp larvae. _ Organism is not affected 0 Braconid wasp Braconid larvae feed on their host and release themselves shortly before reaching the pupae stage of development. Organism benefits

• There are three major types of symbiotic relationships. – Parasitism meet their needs as ectoparasites (such as leeches) and endopaasites (such as hookworms)

KEY CONCEPT Each population has a density, a dispersion, and a reproductive strategy.

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.

Geographic dispersion of a population shows how individuals in a population are • Population dispersionspaced. refers to how a population is spread in an area. Clumped dispersion Uniform dispersion Random dispersion

• There are three types of dispersion. – clumped

• There are three types of dispersion. – uniform

• There are three types of dispersion. – random

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.

• Survivorship curves can be type I, II or III. – – Type I—low level of infant mortality and an older population common to large mammals and humans Type II—survivorship rate is equal at all stages of life common to birds and reptiles – Type III—very high birth rate, very high infant mortality – common to invertebrates and plants

KEY CONCEPT Populations grow in predictable patterns.

• Changes in a population’s size are determined by immigration, births, emigration, The size of a population and deaths. is always changing. • Four factors affect the size of a population. – – immigration births emigration deaths

Population growth is based on available • Exponential growthresources. is a rapid population increase due to an abundance of resources.

• Logistic growth is due to a population facing limited resources.

• 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.

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.

• Density-dependent limiting factors are affected by the number of individuals in a given area. – predation – competition – parasitism and disease

• Density-independent limiting factors limit a population’s growth regardless of the density. – unusual weather – natural disasters – human activities

KEY CONCEPT Ecological succession is a process of change in the species that make up a community.

Succession occurs following a disturbance in an ecosystem. • Succession regenerates or creates a community after a disturbance. – a sequence of biotic changes – damaged communities are regenerated – new communities arise in previously uninhabited areas

• There are two types of succession. – primary succession — started by pioneer species

• There are two types of succession. – secondary succession — started by remaining species