Ecology and Evolution Notes

8/8/2019 Ecology and Evolution Notes

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Ecology- oikos meaning home and logos meaning study- studying the external environment of species- study of interactions between biotic and abiotic factors, which compose the environment

and the organisms- study of the distribution and abundance of organisms

Environment: biotic

other organismsAbiotic physicochemical factors

Habitat: where an organism livesNiche: functional role of an organism in the environment

a) fundamental- main role; i.e. worker bees-protect queenb) realized- role determined by the environment and condition; i.e. worker bees-make honey

and pollinate flowers*another example: interaction between Balanus and Cthalamus barnacles.

Interaction: flow of matter and energy*food chain and food web

1. Primary productivity: rate at which plants assimilate solar energy in a particular community2. Secondary productivity: rate of biomass production by heterotrophs or consumers

GPP: gross primary productivityNPP: net primary productivity

=GPP-RR: respiration

Plant and animal associations:

diversitydominance

Species diversity: total number of all the different species in the area

Species richness: relative abundance of different species in the area

Species evenness: number of individuals per species

Even diverse richness. Richness may imply diversity, but they are not equal terms

Ecological population: same species occupying the same area over the same time

Demography: study of population change throughout an organisms life-mortality rates, birth rates, immigration, emigration

Life table: the summary of stages or age groups related to the survivorship of an organism.a)Dynamic: age-specific; short-lived individuals i.e. insects

*cohort-single generation observed in the life tableb)Static: time-specific; long-lived individuals i.e. humans

Survivorship curvesa) Type I: for long-lived organismsb) Type II: ideal and limitedc) Type III: for short-lived organisms

Environment Organismmodifies

shapes


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Population growth1) Exponential growth: geometric increase in population size

-J-shaped curve in a rate vs. number of individuals plot-common among r-selected organisms

2) Logistic growth: growth rate levels off as it reaches K (carrying capacity)-S-shaped curve-common among K-selected organisms

**r-selected: short-lived organisms with short life span, but are fast reproducers; pioneer communitiesi.e. grass, rats, insects

**k-selected: long-lived organisms with long life span with long maturation time; climax communitiesi.e. trees, humans, higher forms of animals

Succession: transition in species composition in a previously disturbed area over time*disturbance: natural or man-made

Steps in succession: colonization site modification change in species composition

Primary succession: succession where the environment at the start is virtually lifelessSecondary succession: succession where the environment previously hosted life (i.e. hay infusion)

Models of succession:1. Facilitation model- linear, unidirectional

2. Inhibition model- no regard in order of succession/occurrence3. Tolerance model- some organisms are not necessarily needed

No. ofsurvivors

age

III

II

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Evolution: change in genetic constitution/ gene frequency of a population through time; or descentwith modification through time

Natural selection: survival of the fittest; differential reproduction of some members of a speciesresulting from variable fitness conferred by genotypic differences

Adaptation: inherited characteristics that help the individual survive and reproduce; these inheritedcharacteristics are favored by the environment during natural selection

Selective factors: significant component of the environment that affect the survival and growth of acertain organism, but not affecting other organisms

**natural selection evolution; natural selection does not necessarily suggest evolution, becauseevolution needs a long time/ many generations to determine whether it is occurring.

1) Convergent evolution: produces analogous structures (same function, different embryonicorigin)

i.e. wings of insects, bats and birds2) Divergent evolution: produces homologous structures; with a common ancestor

i.e. limbs

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Ecology and Evolution Notes