Unit 8: Ecology

Type 1 survivorship curves

represent populations whose organisms tend to survive beyond their young and middle-ages and die when they become elderly (usually have small numbers of offspring and lots of parental care - steady then sharp decrease)

Type 2 survivorship curves

represent populations with a constant proportion of individuals dying at each age interval (usually few offspring with lots of parental care - constant slope)

Type 3 survivorship curves

represent populations that have a high death rate among the young but a lower death rate among the middle/old age (usually have many offspring with low parental care - sharp decrease then steady)

abiotic factors

non-living components of ecosystem (eg. air, water, soil)

biotic factors

living components of ecosystem (eg. trees, bacteria, animals)

energy flow

transfer of energy between organisms in an ecosystem

food chains vs food webs

food chain only shows energy flow between one organism to another; food web is composed of many different food chains that intertwine

limiting factors

anything that can limit the size of a population, both living and nonliving (eg. natural disasters, competition, predation, disease)

carrying capacity

largest number of individuals of a particular species that an ecosystem can support over time

symbiosis

any close relationship between different species - mutualism, commensalism, parasitism

mutualism

both species benefit from relationship (eg. bees pollinating flowers)

commensalism

one species benefits and other remains neutral from relationship (eg. remora hanging on shark)

parasitism

one organism benefits and other is harmed from relationship (eg. fleas on dog)

ecological hierarchy

individual; population; community; ecosystem; biosphere

individual level

focus is to examine adaptations that allow organisms to optimize survival and reproduction

population level

consists of all indviduals belonging to same species within a given area

community level

collection of populations in a given area that interact with each other

ecosystem level

comprised of multiple communities and the abiotic environments (sunlight, water, temperature, etc.)

biosphere level

highest ecological level, includes all ecosystems on Earth

most important laws governing ecological succession

laws of conservation of matter and conservation of energy (energy can’t be created/destroyed, only transformed from one form to another - loss of heat)

stimulus

something that evokes a functional reaction

kinesis

random movement toward/away from environmental stimuli

taxis

directional (purposeful) movement toward/away from environmental stimuli

communication

transfer of information between 2 individuals (sender and receiver)

How do species communicate?

visual; chemical; auditory; electrical; tactile

How does communication increase the fitness of an individual?

reproduction; obtaining food

innate behavior

instinctive behavior performed without any previous experience

learned behavior

genes that are necessary to perform the behavior and the individual experience in the environment are acquired through interaction, communication, and experience

energy

the ability to do work - influences quality of living beings: metabolism

thermoregulation

process of organism controlling its body temperature

ectotherms

body temperature is regulated externally (eg. reptiles)

endotherms

body temperature is regulated internally (eg. humans)

What does a net gain of energy allow for?

growth, reproduction - population increase

What does a net loss of energy result in?

no growth/reproduction - population decrease

How is the law of thermodynamics related to trophic levels?

energy availability decreases as you go up trophic levels, lost in the form of heat (most availability at the primary producer level)

energy flow vs matter cycle

energy flows unidirectionally from the sun; matter cycles directionally (eg. carbon cycle)

population size

number of individuals in a given area (assumed same species)

motile species

able to move or be moved independently

How to calculate a population’s size

+ births/immigration, - deaths/emmigration; for a motile species, mark-and-recapture method

mark and recapture method

N = (C/R) x M

population density

number of individuals in a given area divided by the specific size of the area

What is population growth determined by?

other factors: distribution (random, uniform, clumped), sex ratio, age, structure, etc.