Unit 8: Ecology

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 factor

A living part of an ecosystem

abiotic factor

physical, or nonliving, factor that shapes an ecosystem

climate

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

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

population growth is described by...

biotic potential, carrying capacity, and limiting factors

population size

symbolically represented by N it is the total number of individuals in the population

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. example: humans

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 example: rodents, invertebrates

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 example: oysters, species with free-swimming larvae

biotic potential

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

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; can be density-dependent or density-independent

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

reproductive success

measure of fitness - how well an organism survives and reproduces

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.

predation

predator totally or partly consumes a plant or other animal

parasite

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

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

mutualism

symbiotic relationship where both species benefit

commensalism

symbiotic relationship where one species benefits while the second is neither helped nor harmed

parasitism

symbiotic relationship where parasite benefits while the host is harmed

coevolution

evolution of one species in response to new adaptations that appear in another species - evolutionary arms race

mimicry

two or more species resemble one another in appearance

ecological succession

change in the composition of species over time; one community is gradually and predictably replaced by another community

primary succession

occurs where no soil was previously present; begins on rock. pioneer species and other plants break down rock into pebbles, then sand, then soil. as organisms die and decompose, it nourishes the soil allowing for more and larger organisms to grow or live in that area

secondary succession

occurs as primary succession, except soil is already present

food chain

linear flow chart of who eats whom example: grass >>> zebra >>> lion >>> vulture

food web

expanded, more complete version of a food chain that shows all major plants in the ecosystem, various animals that eat them, and the animals that eat the animals

autotrophs

obtain energy from light or inorganic material

heterotrophs

consumer other organisms for organic material and/or a source of energy

ecological pyramids

show relationships between trophic levels, typically showing relationships in energy or biomass

trophic level

an organism's place in a food chain or food web

primary producers

autotrophs that perform photosynthesis

primary consumers

herbivores, heterotrophs that eat primary producers

secondary consumers

carnivores/omnivores, heterotrophs that eat primary consumers

tertiary consumers

carnivores/omnivores, heterotrophs that eat secondary consumers

quaternary consumers

carnivores/omnivores, heterotrophs that eat tertiary consumers

detritivores (decomposers)

heterotrophs that obtain their energy by consuming dead plants and animals (detritus)

why will you typically not see more than five levels in a food chain, pyramid, or web?

only 10% of the energy at one trophic level is available for the next trophic level. 90% of the energy is used, stored, or lost. there's not enough energy in any ecosystem to support more than 5 levels. this is called ecological efficiency.

primary productivity

amount of organic matter produced through photosynthetic activity per unit of time

dominant species

most abundant species or species that contributes the greatest biomass to a community

keystone species

one that has a strong influence on the health of a community or ecosystem; removal of a keystone species results in dramatic changes in the makeup of species that comprise other trophic levels

invasive species

introduced species that proliferates and displaces native species because it is a better competitor or because its natural predators or pathogens are absent

biodiversity

function of the number of species, niches, and trophic levels in the ecosystem and the complexity of its food web

biogeochemical cycles

describe the flow of essential elements from the environment to living things and back; elements are stored in reservoirs and assimilated into organisms as well as released back into the environment (water, carbon, nitrogen, phosphorus)

humans damage the biosphere by...

exponential population growth habitat destruction pollution

most destructive consequences of human activity include...

global climate change, deforestation, acid rain, reduction in species diversity, ozone depletion, desertification, and pollution

global climate change

Burning of fossil fuels releases greenhouse gases such as carbon dioxide into the atmosphere. These greenhouse gases trap infrared radiation, raising the temperature of the earth's atmosphere and resulting in large scale climate change.

acid rain

burning of fossil fuels like coal and other industrial processes release pollutants in the air, which react with water vapor to produce sulfuric acid and nitric acid, which rains down on us

desertification

overgrazing of grasslands that border deserts transform those grasslands into deserts; agricultural output decreases and habitats available to native species are lost

deforestation

clear-cutting of forests causes erosion, flooding, and changes in weather patterns; occurs most often in the tropical rainforest, where most of our carbon fixation occurs

nitrogen cycle

The movement of nitrogen from the atmosphere to the soil, to living organisms, and back to the atmosphere; including the processes of nitrogen fixation and decomposition.

nitrogen fixation

the chemical processes by which atmospheric nitrogen is assimilated into organic compounds (that plants can use), especially by certain microorganisms as part of the nitrogen cycle.

carbon cycle

the movement of carbon from the nonliving environment into living things and back

10% rule

Only 10% of the total energy at each trophic level is available to the next level. The amount of energy passed up to the levels of the food pyramid reduces as you go up.

Simpson's Diversity Index

a measure of diversity between similar ecosystems ( N-(N-1) ) / ( total n (n-1) ) N = total number of organisms n = number of individuals of each species