IB Biology HL Unit 5

ecology

study of interactions among and between organisms and their physical environment

6 levels of ecological organization

• individual

• population

• community

• ecosystem

• biome

• biosphere

population

group of organisms of same species living in same area at same time

community

all of the populations living together in defined area

biotic factors

living things

abiotic factors

nonliving things

ecosystems

all biotic and abiotic factors

biome

group of ecosystems that share similar climates and typical organisms

biosphere

entire planet w/ everything

open system

energy and matter enters/exits naturally or bc of human involvement

closed system

only energy can enter/exit

example of open system

• ecosystem

examples of closed system

• biosphere 2

• mesocosm

autotroph (producer)

make own organic molecules for ATP

photoautotrophs

make own organic molecules using light

heterotroph

obtain organic molecules from other or

4 types of heterotrophs

• herbivore

• carnivore

• omnivore

• scavenger

• decomposer

scavenger

consumes carcasses killed by predators or died of other causes

decomposer

extract energy by breaking down dead

2 types of decomposers

• sapotroph

• detritivore

sapotroph

obtain organic nutrients thru external digestion from dead organisms

• secrete hydrolytic enzymes to break down large molecules outside organism and absorb smaller nutrients

detritivore

obtain nutrients from detritus using internal digestion

detritus

organic matter created during decomp of dead

food web

show flow of energy/bioass thru community

food web

several interconnected food chains

5 trophic levels

• producer

• primary consumer

• secondary consumer

• tertiary consumer

• quaternary consumer

10% rule

on average, only 10% of available energy at lower trophic level can be transferred to next trophic level

• limits food chain length

5 sources of energy loss

• heat dissipation

• incomplete consumption

• inefficient digestion

• used in metabolic processes

• inefficient energy conversion/storage

energy pyramid

represents # of energy available per trophic level in energy units per area per time

biomass

total dry mass of a group of organisms in area/volume

• contain energy

primary productivity

rate at which consumers accumulate carbon compounds in biomass

• increases with increased biodiversity and # of consumers in ecosystem

• measured in mass per unit area per unit time

secondary productivity

rate at which consumers accumulate carbon compounds in own biomass

net (secondary or primary productivity) equation

net = gross - R

• R = loss of energy due to respiration

carrying capacities

max pop size of a species that can be sustained long term by a given environment

limiting factors

environmental factors that restrict growth, distribution, abundance of a population/organism in an ecosystem

examples of limiting factors

• availability of food/water

• space

• shelter

• disease

• parasite

• predation

• climate/weather

density dependent limiting factors

have increased impact on pop size as pop density increases

• due to increase in interspecific and intraspecific competition

• maintains carrying capacity

interspecific competition

competition between organisms of diff species

intraspecific competition

competition between organisms of same species

examples of density dependent limiting factors

• comp for resources

• predation

• disease

• parasite

density independent limiting factors

impact regardless of density

• external, typically abiotic factors

examples of density independent limiting factors

• natural distrurbances

• anthropologic events (habitat destruction, pollution, climate change)

two types of population growth curves

• exponential pop growth

• sigmoid pop growth

exponential population growth

occur in ideal conditions, favorable factors, unlimited resources

• j shaped curve

• prevented in ecosystems by limiting factors

example of exponential population growth

American Plains Bison in Yellowstone

• 1902: 21 remain → 1915: 250

sigmoid population growth

occur in environment w/ limited resources

• s shaped curve

• 3 phases

3 phases of sigmoid population growth

• exponential growth

• transitional phase (growth slows)

• plateau phase (carrying capacity

4 factors affecting population growth

• natality

• mortality

• immigration

• emmigration

population growth equation

pop growth = (N + I) - (M + E)

intraspecific interactions

interactions between organisms of same species

2 types of intraspecific interactions

• intraspecific competition

• intraspecific cooperation

intraspecific competition

competition between same species

• density dependent

intraspecific cooperation

collab between a species

interspecific interactions

interactions between diff species

community

interacting but diff species in particular area

herbivory

feeding relationship where herbivore eats plant

predator prey relationship

• density dependent, cyclical pattern

• prey increase →pred increase →increase predation → decrease prey → decrease food for pred → decrease pred → less predation → increase prey → repeat

• slight lag time

interspecific competition

comp between diff species for same resources

• ex: eastern grey squirrel and American red squirrel

how to test for interspecific comp

remove 1 species from ecosystem

if other species thrives and increase success → interspecific comp

symbiotic interactions

2 organisms living/interacting w/ each other where at least 1 organism benefits

3 types of symbiotic interactions

• parasitism

• commensalism

• mutualism

parasitism

parasite is helped, host is harmed

• ex: tapeworm in human gut

pathogen

microorganism/virus causes disease in host (pathogenicity)

• diff from parasitism bc host is normally directly/immediately harmed and spread is more rapid

commensalism

1 organism is helped and other isn't harmed or helped

• ex: orchids on tree branch

mutualism

both organisms helped

3 examples of mutualism

• root nodules in legumes

• mycorrhizae in orchids

• zooxanthellae in hard corals

root nodules in legumes

• root nodules have nitrogen fixing bacteria giving legumes useful nitrogen

• legumes provide bacteria w carbs/compounds-

mycorrhizae in orchids

• fungi colonize orchid roots and form mycorrhizae → increase SA for nutrients

• orchids give fungi organic compounds from photosynthesis

zooxanthellae in hard corals

• zooxanthellae (unicellular photosynthetic algae living in hard coral tissue

• coral give shelter and access to sun

• zooxanthellae give organic molecules from photosynthesis and pigment to protect from UV exposure

endemic species

native to location

introduced (alien) species

non native and introduced by humans

• some don’t become invasive

invasive

harm ecosystem, outcompete native spevies

• ex: Kudzu in GA

Kudzu in GA

native to Japan and China, introduced in US in 1976 as ornamental plant and promoted as tool to prevent soil erosion in 1930s-1950s

• grows 1ft/day → outcompete native plants → loss of nature biodiversity

• invasive species example

top down control

presence/activity of organisms at increased trophic levels regulate abundance/behavior of lower levels of food chain

• ex: wolves of yellowstone

Wolves of Yellowstone

reintroduction of grey wolves → trophic cascade

• top down control example

trophic cascade

impact other trophic levels

bottom up control

availability of resources at lower trophic levels influence abundance/distribution of organisms at higher trophic levels

• ex: nutrients in soil

allelopathy

organisms release biochemical compounds into environment influencing growth/survival/reproduction of other organisms

• ex: black walnut tree roots

bklack walnut tree roots

• release tosic chemicals killing nearby plants

• example of allelopathy

antibiotic secretion

some microorganisms (fungi/bacteria) secrete antibiotics to hinder bacterial growth

• ex: streptomyces bacteria

streptomyces bacteria

synthesize wide range of antibiotics including streptomycin

• example of antibiotic secretion

• often in soil/marine environment

adaptations

characteristic aiding survival specific to environment

• help cope w abiotic and biotic factors

habitat

place organism lives and interacts

• defined by geographical and physical location

Marram grass

• adapted on sand dunes to drought and sand tolerance, strong roots and leaves, rhizomes

rhizomes

horizontal underground roots

Rhizophora apiculata

• halophyte

• adapted to live on mangroves: high salinity and in brackish water

• pneumatophores provide plant w O2 in water logged soil

halophyte

plant species that can survive in high salinity

brackish water

where saltwater and freshwater mix

pneumatophores

specialized aerial roots

range of tolerance

range of tolerable conditions based on species adaptations

• outside of tolerance = limiting factor

biome

group of similar ecosystems w common abiotic/biotic factors

terrestial biomes

dominant vegetation, animals, and climate patterns characterize it

2 main abiotic factors that determine biome type

• rainfall

• temperature

climograph

shows average rainfall and temp and according biome type

adaptations for plants in hot deserts

• deep roots

• shallow horizontal roots

• chlorophyll in bark

• thorny stem

adaptations for animals in hot deserts

• store fat

• slow metabolism

• skin covering

• moisture retainance thru organs

adaptations for plants in tropical rainforest

• large leave

• waxy cuticle

• root system extract nutrient

adaptations for animals in tropical rainforest

• prey catching/predation avoiding adaptation

• climbing adaptation

• navigation adaptation

ecological niche

organism’s role in ecosystem

• includes habitat and interactions and impact

specialist species

• live in specific conditions

• highly specialized niche

• ex: koala