Unit Eight: Ecology

ecology

study of the distribution and abundance of organisms and their interactions with other organisms and with their physical environment

population

group of individuals of the same species living in the same area

community

group of populations of different species living in the same area

ecosystem

interrelationships between organisms in a community and their physical environment

biosphere

composed of all the regions of the earth that contain living things (hydrosphere, geosphere, and atmosphere)

habitat

type of place where an organism usually lives; descriptions typically include the organisms and the physical and chemical characteristics of the environment

niche

all biotic and abiotic resources in the environment used by an organism

biotic

living

abiotic

nonliving

climate

long-term prevailing weather conditions in a given area; major components include temperature, precipitation, sunlight, and wind

macroclimate

global, regional, or local climate

example: changing angle of earth with respect to the sun, bodies of water, mountains that exert long-term effects

microclimate

fine-scale variations, like sunlight and temperature under a log

biome

large region of the earth whose distribution depends on the amount of precipitation and temperature in an area; characterized by dominant vegetation and animal life

major biomes of the world

tropical rainforest, temperate grasslands, conifer forest (taiga), desert, temperate deciduous forest, tropical seasonal (dry) forest, tundra, savanna, chaparral, and aquatic biomes

tropical rainforest

abundant rainfall, stable temperature, high humidity

most biodiversity of any biome

desert

little to no rainfall, greatly varying temperatures, no humidity

temperate grasslands

covers huge areas in temperate and tropical regions of the world

temperate deciduous forest

trees drop their leaves in winter

conifer forest/taiga

dominated by conifer forests

tundra

characterized by permafrost

savanna

grasses and some trees

chaparral

dominated by dense, spiny, evergreen shrubs

aquatic biomes include...

freshwater, estuaries, marine

primary way to distinguish aquatic biomes

salinity

vertical stratification in aquatic biomes

photic zone: enough light for photosynthesis

thermocline

narrow layers of fast temperature change that separate a warm upper layer of water and cold deeper waters

littoral zone

in fresh, standing bodies of water, it is the well-lit shallow water near the shore that contains rooted and floating aquatic plants

limnetic zone

in fresh, standing bodies of water, it is the well-lit open surface waters farther from shore that are occupied by phytoplankton

oligotrophic lakes

deep lakes that are nutrient-poor, oxygen-rich, and contain sparse phytoplankton

eutrophic lakes

shallower, higher-nutrient content, lower oxygen content, high concentration of phytoplankton

primary way to characterize moving bodies of water

current

marine biome

largest and most stable biome

temperature varies little because of water's high heat capacity

marine biome zones

intertidal zone: land meets water, as in tide pools

neritic zone: beyond intertidal zone; shallower water over continental shelves

population ecology

study of the growth, abundance, and distribution of populations

population growth is described by...

biotic potential, carrying capacity, and limiting factors

population size

symbolically represented by N

population density

total number of individuals per area or volume occupied

population dispersion

describes how individuals in a population are distributed

clumped dispersion

most common pattern, like humans in cities or schools of fish

uniform dispersion

like trees in an orchard, or plants with toxins

random dispersion

like trees in a forest; occurs because of special attractions or repulsions

age structure

describes the abundance of individuals of each age

survivorship curves

describe how mortality of individuals in a species varies during their lifetimes

type I survivorship curve (K- strategist)

describe a species in which most individuals survive to middle age; after that age, mortality is high.

type II survivorship curve (c- strategist)

describe organisms in which the length of survivorship is random, that is, the likelihood of death is the same at any age

type III survivorship curve (r-strategist)

describe species in which most individuals die young, with only a relative few surviving to reproductive age and beyond

biotic potential

maximum growth rate of a population under ideal conditions with unlimited resources and without any growth restrictions

factors that contribute to biotic potential

age at reproductive maturity, clutch size, frequency of reproduction, reproductive lifetime, survivorship of offspring to reproductive maturity

carrying capacity

maximum number of individuals of a population that can be sustained by a particular habitat

limiting factors

elements that prevent a population from attaining its biotic potential

types of limiting factors

density-dependent factors and density-independent factors

density-dependent factors

limiting effect becomes more intense as the population density increases

examples: parasites and disease, competition, toxic effect of waste products, predation, stress

density-independent factors

occur independently of the density of a population

examples: natural disasters and climate extremes

r-strategist

(or r-selected species)

rapid, exponential growth

quickly invade a habitat, quickly reproduce, then die

offspring are small, quickly maturing, and require little to no parental care

k-strategist

(or k-selected species)

slower, logistic growth

size of mature population remains relatively constant

small number of large offspring

extensive parental care

reproduction repeats throughout lifetime

exponential growth

occurs when reproductive rate is greater than zero; forms a J-shaped curve on a graph

logistic growth

occurs when limiting factors restrict the size of a population to the carrying capacity of the habitat; forms an S-shaped curve on a graph

life history

describes an organism's strategy for maximum fitness

reproductive success

measure of fitness - how well an organism survives and reproduces

reproductive success depends on four variables

age of reproductive maturity

frequency of reproduction

number of offspring per reproductive event

how long the organism lives

community ecology

concerned with the interaction of different populations

interspecific competition

competition between two different species via...

- competitive exclusion principle (Gause's principle)

- resource partitioning

- realized niche

- character displacement (niche shift)

Competitive Exclusion (Gause's principle)

when two species compete for exactly the same resources, or occupy the same niche, one is likely to be more successful

resource partitioning

some species coexist in spite of apparent competition for the same resources. they actually occupy slightly different niches.

fundamental niche

niche that an organism occupies in the absence of competition

realized niche

when competitors are present, one or both species may be able to coexist by occupying realized niches. here, any niche overlap is absent. they do not compete for the same resources.

character displacement

niche shift

certain characteristics may enable individuals to obtain resources in their partitions more successfully. this reduces competition and leads to a divergence of features.

predation

predator totally or partly consumes a plant or other animal

true predator

kills and eats other animals

parasite

spends most or all of its live living on or in a host; obtains nourishment by feeding on host tissues

parasitoid

insect that lays eggs on a host, usually an insect or spider, and after hatching the larvae consume the host

herbivore

animal that eats plants; some act like predators and totally consume the organism whereas others may only eat a part of the plant

symbiosis

two species that live together in close contact during a portion or all of their lives

types of symbiotic relationships

mutualism

commensalism

parasitism

mutualism

both species benefit

commensalism

one species benefits while the second is neither helped nor harmed