TTM AP bio ecology

levels of organization

individual (single organism)
population (group of organisms of same species in given area)

community (all the population of species, all biotic)

ecosystem (biotic community + abiotic factors that affect it)
biome (group of ecosystems with same climate, similar communities)

biosphere (layer of Earth that supports life; high in atm to deep in ocean)

niche

the role or position that an organism has in an ecosystem

• can be how it meets its need for food

  • what does it eats, when and how it obtains its food, what is its role in energy flow of the ecosystem, shelter, reproduction, care for offspring

biodiversity

the variety of life in an area

• Determined by the number of different species in that area

• biodiversity encompasses the genetic variety within each species and 

• the variety of ecosystems that species create.

• High biodiversity = healthy ecosystem

population distribution patterns

clumped - Due to attraction between individuals or attraction of individuals to a common resource

random - due to neutral interactions between individuals, and between individuals and local environment

uniform - due to antagonistic interactions between individuals or local depletion of resources

factors that can affect species distribution and abundance

• species-specific catastrophes

• environmental catastrophes

• geological events

• sudden influx/depletion of abiotic resources

• increased human activities

factors limiting growth

exponential growth limited bc of
limiting factor - biotic/abiotic factors that restrict the number, distribution, or reproduction of pop within a community
tolerance - an organism’s ability to survive biotic and abiotic factors

density-dependent factors + graph

predation: more likely for predator to find you

disease: disease spreads more quickly

competition: more demand for resources

parasitism: higher infection rates

will usually have logistic type growth, limited by carrying capacity

density-independent factors

storms or natural disasters, extreme heat or cold, rainfall (drought), seasonal cycles

exponential vs logistic growth + formulas

exponential: no constraints on pop, theoretical if unlimited resources
logistic - realistic, presence of limiting factors

biotic potential

The highest rate of natural increase for a population, when resources are unlimited

• pops rarely reach their biotic potential bc resources are usually limited

carrying capacity

sustainable abundance of a species that can be supported by the ecosystem’s total available resources (represented by K)

cohort

all members of a population born at the same time

survivorship curves

type 1: most individuals live out their lifespan and die of old age (k-spec)
type 2: individuals die at a constant rate across their lifespan

type 3: most individuals die early in life (r-spec)

age distribution patterns

pyramid shape - indicate the population has high birthrates, is undergoing exponential growth

bell shape - characteristic of stable populations

urn shape - birthrate falling below the death rate of characteristic of declining populations

r-selected vs k-selected

R: high rate of population increase

• ex. bacteria, algae, insects, annuals

K: reproduce late in life and have a small number of offspring with long life spans

• ex. large mammals, long lived plants

rmax formula

r - (Births - deaths) / Pop size

species richness

a listing of the species within a community; it does not reveal the relative abundance of organisms

ex. a coniferous forest has a different composition from a tropical rain forest in species of plants and animals

species diversity

not only the listing of the species in the community but abundance of each species

• the greater the diversity, the greater the number and the more even the distribution of the species

Simpson diversity index

closer to 1, the more diverse the community is

- takes into account both species richness and species evenness

keystone species

• help determine the types and numbers of other species in a community.  

• have a much larger effect on the types and abundances of many other species in a community than their number would suggest

competition

(-/-): the interaction is detrimental to both species

• between 2 different species

  • interspecific competition 
    

• if it is between 1 species.

  • intraspecific competition 

effects:

• competitive exclusion: principle states that two species competing

• leads to resource partitioning: when species shift niches, they no longer directly compete

Predation

(+/-): the interaction is beneficial to one species and detrimental to the other

Mutualism (symbiosis)

(+/+): obligate symbionts: both organisms entirely depend on each other for survival

Commensialism (symbiosis)

(+/0): benefits one organism, the other organism is not affected

parasitism

(+/-): benefits one organism, harms the other organism

• organism that benefits is called the parasite

• organism that is harmed is called the host

fundamental vs realized niche

fundemental - full potential role of an organism with NO competition

realized - actual role when you include competition and predation —> resource partitioning

chemical animal defenses

taste bad, poison & stings

animal defenses against predators

defensive coloration: aposematic coloration (warning coloration)

• individuals advertise poisonous nature

cryptic coloration: camouflage (blending coloration)

animal defenses: mimicry

mullerian mimicry: deceptive relationship where a harmless species (mimic) copies a dangerous one (model) to avoid predators

basterian mimicry: mutualistic relationship where two or more unpalatable/dangerous species share similar warning signals, strengthening protection for all.

predator/prey population changes

describe the interaction where one species (predator) consumes another (prey), influencing population dynamics and evolutionary adaptations; predator often lagging behind prey in peaks

• The biotic potential of the predator may be great enough to overconsume the prey; the prey population declines and the predator population then follows

• Or the biotic potential of the prey is unable to keep pace and the prey population overshoots the carrying capacity and suffers a crash

climax community

Communities that are more diverse in species types and ages are better able to withstand changes

• have more complex food webs

• resource partitioning/stable realized niches

• reduced competition

• high tolerance to ecological disturbance

• vegetation is perennial

pioneer communities

Communities that are low in diversity in species types and ages are characteristic

• have very simple food chains

• high competition

• vegetation is annual

top down vs bottom up control

top down: organisms higher up in the food web will determine the population size at each level (herbivore controls plant pop)

bottom up: organism lower in the food web will determine the population size at each level (scarce soil nutrients limit plant growth)

Factors affecting species diversity in communities

• Latitude 

• Habitat diversity

• Time

• Habitat disturbance

• Biogeography

• Pollution

primary vs secondary succesion

primary - no intact soil, restart

secondary - intact soil

biomass + energy pyramids

pyramid of energy: An average of 10% of energy is transferred from one trophic level to the next

pyramid of biomass can either mirror the energy pyramid (as for the abandoned field) or be inverted (as for the ocean).

limit of food chains: energetic hypothesis & Dynamic Stability Hypothesis

energetic hypothesis: only enough energy to support a certain number of links

Dynamic Stability Hypothesis: The longer a food chain, the less stable it is. Population fluctuations at lower trophic levels are magnified at higher levels, making top predators vulnerable to extinction.

chemosynthesis

process by which specific microorganisms prepare food (glucose) using inorganic substances without sunlight. They rely on the oxidation of sulfur, hydrogen, hydrogen sulfide, and methane for their energy source.

biomagnification

higher trophic levels even more effected in toxins accumulated from lower trophic levels

niche partitioning types

spatial, Dietary, by resource height, temporal

energy flow in ecosystems

Energy flows, not cycles; but matter cycles

energy must be constantly input to an ecosystem

• autotrophs/producers capture energy and use it, energy passed on to heterotrophs (need source of preformed organic material)

  • heterotrophs include decomposers

limiting nutrient

element that must be added for production to increase. The nutrient most limiting marine production is nitrogen and phosphorus.

biogeochemical cycles: nutrients cycles involve both biotic and abiotic compounds

carbon cycle

• all organisms put out carbon dioxide into the atmosphere (respiration, some fermentation)

• living and dead organisms act as reservoirs for carbon: they contain organic carbon

• human activities increase the level of CO2 (burning fossil fuels), contributing to climate change

carbon fixation

the initial phase of the Calvin cycle where inorganic carbon dioxide (CO2) is attaches to an organic molecules, rubisco. The process converts inorganic carbon into organic compounds (3PGA) in the stroma of chloroplasts, crucial for producing sugars.

nitrogen cycle

• nitrogen gets passed through the food web, plants have nitrogen —> animals and decomposers use

• any nitrogen that is released into atmosphere cannot be used by organisms, so bacteria fixes nitrogen into usable form

  • in root nodules of legumes

  • other bacteria change nitrogen from ammonium into nitrites then nitrates for assimilation

• this is why we need crop and legume rotation

• humans increase rates in nitrogen cycle through fertilization, runoff —> algae blooms

nitrogen cycle processes

nitrogen fixation: N2 to ammonium via nitrogen fixing soil bacteria

nitrification: bacteria convert ammonium into nitrites then nitrates

assimilation: plants absorb nitrates from their roots and use it for proteins + nucleic acids, animals obtain nitrogen by eating them

ammonification: when plants/animals die or produce waste, decomposers decompose organic nitrogen back into ammonium

denitrification: denitrifying bacteria convert nitrates back into nitrogen gas, returning it to the atmosphere

phosphorus cycle

• Geological upheavals move phosphorus from the ocean to land

• Slow weathering of rocks returns phosphorus to the soil

• Most phosphorus is recycled within a community

• Phosphorus is a limiting nutrient

eutrophication

excess N and P from agricultural runoff —> enters waterways —> algal bloom —> algae die —> aerobic bacteria decompose them —> reduces oxygen in water —> biodiversity dies

invasive species

• cause disease

• act as predators or parasites

• acting as competitors

• altering habitat

• hybridizing with local species

prevent by: inspect imported goods likely to contain invader species, international laws banning transfer of invader species

indicator species

serve as early warning of damage or danger to a community

direct human alterations of ecosystems

• habitat loss due to logging, agriculture, livestock farming, urbanization

• introducing new/exotic/invasive species

• overharvesting wild plants and animals

• pollution: pharmaceuticals & microplastics

• logging, urbanization, monocropping to eutrophication

indrect human alterations of ecosystems

global climate change, which alters ecological systems and reduces Earth’s capacity to sustain life

Monocropping

gricultural practice of growing a single crop year after year on the same land, without rotation through other crops

→ Depletes soil of nutrients

→ Creates an ideal niche for parasites and pests (food bonanza)

→ Requires more fertilization and pesticide use 

3 types of ecological extinction

Local extinction: when a species is no longer found in an area it once inhabited, but is still found elsewhere in the world.

ecological extinciton: occurs when so few members of a species are left that it can no longer play its ecological roles in the biological community.

Biological extinction: when a species is no longer found anywhere on earth…this is FOREVER!

HIPPO causes of extinction

habitat fragmentation

invasive species

human population growth

pollution

other: poaching, overhunting, overharvesting, climate chnage

effects of global climate change (direct)

• rising maximum temperatures (NASA Climate Change, 0:36min)

• rising minimum temperatures 

• more intense floods, droughts, intense rainfalls, more frequent and severe heat waves

• snow and rainfall patterns shifting

• rising sea levels 

• higher ocean temperatures 

• shrinking glaciers

• thawing permafrost

effects of global climate change (indirect)

• increasing spread of pests and pathogens

• loss of biodiversity due to limited adaptability

• ocean acidification due to increased HCO3 concentrations in the water as a consequence of increased CO₂ concentrations

• an increase in hunger and water crises, especially in developing countries