Interactions of Organisms in Ecosystems (Unit 3 – LT)

KEY CONCEPT Every organism has a habitat and a niche.

A habitat differs from a niche.

Habitat• The area or environment where an organism or

ecological community normally lives or occurs:

Marine habitat

Niche >Rhymes with itch!

The functional role of a species in its environment‚ includes:

Clown fish living among the tentacles of a sea anemone.

Food- how it fits in a food web

Behavior-interaction with other organisms and environment

Abiotic conditions it can tolerate.

I think of my niche as my job!

KEY CONCEPT Organisms interact as individuals and as populations.

Competition and predation are two important ways inwhich organisms interact.

Competition• Competition occurs when two organisms compete for the

same resource.

Interspecific Competition involving different species

Intraspecific Competition involving the same species

Predation

occurs when one organism captures and eat another.

Symbiotic Relationships or Symbiosis

Symbiosis is a close ecological relationshipbetween the individuals of two (or more) different species.

There are three major types of symbiotic relationships.

Mutualism:

. both organisms benefit

+

+

+

+

Bat eats nectar.

Cactus is pollinated. +

Organism benefits

++

Organism benefits

- one organism benefits, the other is unharmed

Human 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 benefits+

Ø

Ø Organism is not affected

Commensalism

Commensalism:

Parasitism:–one organism benefits, the other is

harmed

Organism benefits+

_

Organism is affected negatively

Hornworm 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++

– Parasites meet their needs as either

Ectoparasites-outside the body of host

Endoparasites- inside the body of host

Leech

Hookworm

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.

• Scientists can calculate population density.

Population Density

• Population dispersion refers to how a population is spread out in an area.

Geographic dispersion of a population shows how individuals in a population are spaced.

Clumpeddispersion

Uniformdispersion

Randomdispersion

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 – One to two offspring – An older population– Slow to reach

reproductive age– Common to large

mammals and humans

Baboon

Type II

– survivorship rate is equal at all stages of life

– Multiple offspring– Reproductive age

usually reached in one or two years

– Common to birdsand reptiles

What ‘ll it be berries or worms?

Feed us now!

Type III

– Very high birth rate

– Very high infant mortality

– Usually reach sexual maturity in one season

– Common to invertebrates and plants

Cicada

KEY CONCEPT

Populations grow in predictable patterns.

The size of a population is always changing.

. Four factors affect the size of a population.–Immigration (in)–Emigration (out)–Births–Deaths

Population Growth

• Population are directly effected by the amount of resources available.

• There are two distinct types of population growth

• Exponential growth is a rapid population increase due to an abundance of resources.

Exponential Growth

Australian farmer introduced 24 rabbits (European) in 1859 today there are ~ 300 million rabbits.

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

Starts slowly then becomes exponential growth but levels off as resources become scarce.

Logistic Growth

• Carrying capacity is the maximum number of individuals in a population that the environment can support.

Carrying Capacity

• A population crash is a rapid decline in the size of a population over a short period of time.

Carrying capacity

Population Crash

Ecological factors limit population growth.

• A limiting factor is “something” that keeps the size of a population down.

Density Dependent Density Independent

• Density-dependent limiting factors are affected by the number of individuals in a given area.

– parasitism – disease

– competition– predation

Density-dependent

• Density-independent limiting factors limit a population’s growth regardless of the density.–unusual

weather–natural

disasters–human

activities

Density-Independent