interactions of organisms in ecosystems unit 3 lt n.
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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: . M arine habitat.

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habitat
Habitat
  • The area or environment where an organism or ecological community normally lives or occurs:

Marine habitat

niche rhymes with itch
Niche >Rhymes with itch!

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

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!

Clown fish living among the tentacles of a sea anemone.

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KEY CONCEPT Organisms interact as individuals and as populations.

Competition and predation are two important ways inwhich organisms interact.

competition
Competition
  • Competition occurs when two organisms compete for thesame resource.
  • Intraspecific Competition involving the same species
  • Interspecific Competition
  • involving different species
predation
Predation

occurs when one organism captures and eat another.

s ymbiotic r elationships or symbiosis
Symbiotic Relationships or Symbiosis

Symbiosis is a close ecological relationship

between the individuals of two (or more) different

species.

There are three major types of symbiotic relationships.

mutualism
Mutualism:
  • both organisms benefit

.

Bat eats nectar.

Cactus is pollinated.

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Organism benefits

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Organism benefits

commensalism

Commensalism

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.

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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.

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Organism is not affected

Organism benefits

Commensalism:
  • - one organism benefits, the other is unharmed
parasitism

Braconid wasp

Braconid larvae feed on their host and release themselves shortly before reaching

the pupae stage of development.

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Parasitism

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Hornworm caterpillar

The host hornworm will eventually die as its organs are consumed

by wasp larvae.

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Organism benefits

Organism is affected negatively

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Parasitism:
  • one organism benefits, the other is harmed
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Parasites meet their needs as either

Ectoparasites-outside the body of host

Endoparasites- inside the body of host

Hookworm

Leech

population density is the number of individuals that live in a defined area
Population density is the number of individuals that live in a defined area.

Population Density

  • Scientists can calculate population density.
geographic dispersion of a population shows how individuals in a population are spaced

Clumped

dispersion

Uniform

dispersion

Random

dispersion

Geographic dispersion of a population shows how individuals in a population are spaced.
  • Population dispersion refers to how a population is spread out in an area.
survivorship curves help to describe the reproductive strategy of a species
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.

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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

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What ‘ll it be berries or worms?

Feed us now!

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
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Type III

  • Very high birth rate
  • Very high infant mortality
  • Usually reach sexual maturity in one season
  • Common to invertebrates and plants

Cicada

the size of a population is always changing
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 Growth
  • Population are directly effected by the amount of resources available.
  • There are two distinct types of population growth
exponential growth
Exponential Growth
  • Exponential growth is a rapid population increase due to an abundance of resources.

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

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

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

carrying capacity
Carrying Capacity
  • Carrying capacity is the maximum number of individuals in a population that the environment can support.
population crash
Population Crash
  • A population crash is a rapiddecline in the size of a population over a short period of time.

Carrying capacity

ecological factors limit population growth
Ecological factors limit population growth.
  • A limiting factor is “something” that keeps the size of a population down.

Density Dependent

Density Independent

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Density-dependent

  • Density-dependent limiting factors are affected by the number of individuals in a given area.
  • competition
  • predation
  • parasitism
  • disease
slide29

Density-Independent

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