Exam 3 - Science, Society, and the Environment I

evolution

change in a kind of organism over time; process by which modern organisms have descended from ancient organisms through generations; originates in genes and often leads to modifications in appearance or behavior

speciation

process by which new species are generated

endemic species

exist nowhere else on the planet; if an event affects region → affects all members of species

(ex: island-dwelling species are at elevated risk of extinction, bc isolated from typical evolutionary pressures like predators)

number of identified species vs. actual number

1.8 million identified; 3—100 million actual

niche

organism’s role in its community; includes resource use + interaction w/ other organisms

population size

number of organisms in an area at a given time; will grow when there’s abundant resources + very few natural enemies

evolutionary change:

takes a long time and helps to protect a population against unique challenges

fossil

imprint of a dead organism in stone; paleontologists can learn when organisms lived by dating the rock layers that contain fossils

carrying capacity

maximum population size of a species that an environment can sustain

naturalists who came up with natural selection

Charles Darwin and Alfred Russel Wallace (1850s)

closely related species that live in different environments tend to

diverge in their traits

(diff. selective pressures → diff. adaptations)

adaptation

a structure, behavior, or physiological process that helps an organism survive and reproduce in a particular environment

genes that lead to better reproductive success will eventually evolve through the entire population

mutations

accidental changes in DNA → give rise to genetic variation

biological evolution

the change over time in populations of related organisms

convergent evolution

unrelated species in similar environments + separate locations acquiring similar traits (similar selective pressures)

how species arise

1. biological evolution

2. establishes the common ancestry of all species

3. pre-existing species changing through time

species

a classification of organism whose members can interbreed and produce fertile offspring

population

a group of individuals within a species that live in the same geographic area

3 observations natural selection is based on

1. organisms face a constant struggle to survive and reproduce

2. organisms tend to produce more offspring than can survive to maturity

3. individuals of a species vary in their attributes

causes of genetic variation

1. mutations (accidental changes in DNA)

2. sexual reproduction (mixing of genetic material)

medical advances resulting from learning about evolution:

1. how infectious diseases spread + gain/lose potency

2. tracking evolving strains of influenza, HIV, etc.

3. detection of evolution of bacteria’s antibiotic resistance

biodiversity

the variety of life across all levels (species, genes, populations, communities)

evolutionary fitness

success in passing genes to the next generation

what generates biodiversity?

evolution

how speciation occurs

reduced gene flow; some parts of the population no longer reproduce with other parts, which prevents the exchange of genes

allopatric speciation

result of speciation in populations that are geographically isolated from one another; eventually populations grow so different, they can no longer mate

sympatric isolation

two subpopulations become reproductively isolated within the same geographic area

phylogenetic trees

how scientists represent history of divergence; constructed by analyzing + external traits of organisms

taxonomists

group species into categories meant to reflect evolutionary relationships

species that are more vulnerable to extinction

small populations, species that are specialized to narrow resources, endemic species that are only found in one area of the world

background extinction rate

average rate at which species become extinct over the long term; usually 1-5 species per year (1-2 species per 1 million species go extinct per year)

number of mass extinctions earth has seen

at least 5; Permian extinction being the worst

(causes: volcanism, asteroid impact, methane releases, CO₂ concentration, global warming, etc.)

ecology

scientific study of interactions among organisms and between organisms and their environment

population

a group of individuals of the same species that live in the same area

community ecology

study of how interactions between species affect community structure and organization

ecosystem ecology

study of energy flow and chemical cycling among the various biotic and abiotic components

biosphere

sum total of all living things and habitats on earth

landscape ecology

examines how ecosystems, communities, and population are distributed across earth

specialists

species with narrow niches

generalists

species that can utilize a wider variety of resources

population ecology

the study of factors that cause populations to increase or decrease

demographers

scientists who study human populations

they track:

• natality

• mortality

• immigration

• emigration

exponential growth

when unregulated populations increase by a fixed percentage each year; J-shaped curve

when exponential growth occurs in nature

when a population is small, competition is minimal, and environmental conditions are ideal

limiting factors

determine the carrying capacity (max. pop. size of a species env. can sustain)

logistic growth

when population growth slows down as it reaches the carrying capacity; produces S-shaped curve

density dependent factors

limiting factors that rise/fall with population density

(ex: predation, disease)

density independent factors

limiting factors that are unaffected by population density

(ex: extreme temperatures, catastrophic natural disasters)

what are life history patterns determined by?

life form, habitat; tradeoffs in different life history traits

"slow" life history

long time to sexual maturity, long life spans, low numbers of offspring, high parental investment

"fast" life history

short time to sexual maturity, short life spans, high numbers of offspring, little parental investment

Type III survivorship

high mortality early on in life, with relatively low rates of death for those surviving; usually r-selected

Type II survivorship

constant mortality rate regardless of age; prey animals (like birds) can follow this pattern of survival

Type I survivorship

usually experience high survival in early and middle life, followed by a rapid decline in later life; usually K-selected

ecotourism

the practice and business of recreational travel based on concern for the environment

Central Case Study

asian carp scandal; catfish farms imported carp to clean up algae and snail infestations; carp escaped and began spreading across the Mississippi valley

species interactions

predation, competition, parasitism

competition

the struggle between organisms to survive in a habitat with limited resources

coexisting species

species alter behaviors to minimize competition, altering their niche

intraspecific competition

competition between members of the same species

interspecific competition

competition between members of different species

competition become more intense when:

populations are more dense

fundamental niche

The full potential range of the physical, chemical, and biological factors a species can use if there is no competition from other species in a niche

Predation

An interaction in which one organism kills another for food.

cryptic coloration

Camouflage; makes an organism difficult to spot.

warning coloration

conspicuous coloration or markings of an animal serving to warn off predators

mimicry coloration

patterns in physical appearance making an organic look like another organism

Parasitism

A relationship between two organisms of different species where one benefits and the other is harmed

Herbivory

interaction in which one animal (the herbivore) feeds on producers (such as plants)

mutualism

relationship between two species where both species benefit

what do food chains consist of?

trophic levels

how much energy is lost as heat at each trophic level?

90%; only have 10% of the energy content, organisms, and biomass compared to the one below them

Biomass

total amount of living tissue within a given trophic level

keystone species

species that influences the survival of many other species in an ecosystem

ecosystem engineers

a keystone species that creates or maintains habitat for other species

what does succession begin with?

pioneer species

primary succession

An ecological succession that begins in an area where no biotic community previously existed

secondary succession

Succession following a disturbance that destroys a community without destroying the soil

introduced species

species moved by humans to new geographic areas, either intentionally or accidentally

how can we respond to invasive species?

control, eradication, or prevention

what two aims may ecological restoration have?

1. restore the functionality of an ecosystem

2. return a community to its "presettlement" condition

biome

group of ecosystems that share similar climates and typical organisms

what exerts the greatest influence over all other climatic factors?

temperature and precipitation

what creates global patterns of biomes?

temperature and precipitation, which are highly correlated with latitude

rain shadow effect

precipitation falls on the windward side of a mountain range; causes lush vegetation & a warm, moist climate on one side, but a desert area on the leeward/downwind side

temperate deciduous forest

at midlatitudes; relatively even precipitation

temperate grasslands

temperature differences between winter and summer and more extreme and rainfall diminishes; not enough water to support trees; biomes are known as prairie or steppe

temperate rainforest

rich in rainfall, but still found in midlatitudes; mostly contain coniferous trees; soils are fertile, but susceptible to erosion if the forests are cleared

tropical rainforests

year round growing; dark, lush vegetation, and highly diverse communities; high number of tree species intermixed at low densities; acidic soils are low in organic matter

tropical dry forest

wet and dry seasons that each occupy half of the year; temperature is consistently warm; leaves are shed during the dry season

savannas

tropical grasslands interspersed with acacias or other trees; herbivores and fire create disturbances; found ind ry tropical areas, including parts of Africa, Australia, and India; distinct wet and dry seasons

deserts

the driest biome, receiving less than 25 cm of rain per year; soils have high mineral and low organic matter content; animals and plants must adapt to minimize water loss; animals often active at night

tundras

very dry but are constantly cold all year; underground soil is permanently frozen, called permafrost; tundras are unoccupied by humans but are the most directly impacted by air pollution and climate change

boreal forests

cold, but receive more precipitation than tundras; they are dominated by few species of evergreen trees; soils are acidic and nutrient-poor

chaparral

found in only a few small patches throughout the world; covered by a dense thicket of evergreen shrubs; fires are frequently climate is influenced by nearby oceans

aquatic biomes

defined by water characteristics; depth, salinity, distance to land

adaptive radiation

an evolutionary pattern in which many species evolve from a single ancestral species

genetic drift

A change in the allele frequency of a population as a result of chance events rather than natural selection.

Microevolution

evolutionary change within a species or small group of organisms, especially over a short period.

Macroevolution

large-scale evolutionary changes that take place over long periods of time