Ap Bio Chapter 53

Front 1

• Biological Community

Back 1

o Assemblage of populations of various species living close enough for potential interaction

Front 2

• Interspecific relationships

Back 2

o Competition, predation, herbivory, symbiosis, disease

Front 3

• Competition

Back 3

→ when species compete for a resource that’s in short supply (-/-)

Front 4

o Competitive exclusion

Back 4

o Competitive exclusion→ when strong competition leads to the elimination of a species

Front 5

• Competitive exclusion principle

Back 5

o Two species competing for the same limiting resources cannot coexist in the same place- one species will eliminate the other
o Two species cannot coexist in a community if their niches are identical (b/c that means they’re competing for the same resources)

Front 6

• Ecological niche

Back 6

o The sum total of a species’ use of biotic and abiotic resources in its environment is the species’ niche
o An organism’s niche is its ecological role, how it fits into an ecosystem
o Ex: the niche of a tropical tree lizard is the temperature range it tolerates, the size of the branches it perches on, the time of day in which it’s active, and the size/kinds of insects it eats
o Two species cannot coexist in a community if their niches are identical (b/c that means they’re competing for the same resources)

Front 7

• Fundamental niche

Back 7

• Fundamental niche→ the niche potentially occupied by that species

Front 8

• Realized niche

Back 8

• Realized niche→ the niche the species actually occupies (may be different from fundamental niche)

Front 9

• Resource partitioning

Back 9

o When competition between species with identical niches does not lead to the elimination of one species, it’s because one of the species’ niche’s was modified
o Evolution by natural selection can result in one of the species using a different set of resources
o Resource partitioning→ the differentiation of niches that enables similar species to coexist

Front 10

• Character displacement

Back 10

o The tendency for characteristics to be more divergent in sympatric populations of two species than in allopatric populations
o Since there’s more competition in sympatric populations, species need to evolve to be different so they can change their niches and survive
o Ex: two kinds of finches can survive by themselves on separate islands and both have small beaks, but when the two finches live on the same island they can’t both have small beaks b/c they’d be competing for the same resources, one has to evolve to have a bigger beak than the other so they won’t compete

Front 11

• Predation

Back 11

o (+/-)- when one species (the predator) kills another species (the prey) for food
o predators have adaptations to help them catch the prey
o prey have adaptations that help them hide from predators

Front 12

• Cryptic coloration

Back 12

o Defense adaptation
o aka camouflage
o helps prey hide from predators

Front 13

• Aposematic coloration

Back 13

o Coloration that indicates the animal is poisonous
o Poison arrow frogs are brightly colored to warn off predators that they are poisonous

Front 14

• Batesian mimicry

Back 14

o When a harmless species mimics a behavior of a harmful species to fool predators
o Ex: when the larva of a hawkmoth puffs up its head and thorax to look like a snake

Front 15

• Mullerian Mimicry

Back 15

o When a harmless species mimics the appearance of a harmful species to fool predators
o Ex: when frogs have bright colors to make it look like they are poisonous

Front 16

• Herbivory

Back 16

o (+/-) interaction
o when herbivores eat plants
o herbivores have the ability to distinguish between poisonous and non poisonous foods as well as find the most nutritious foods
o herbivores eat specific plants
o use sense of smell or sensors on their feet to figure out which plants they want to eat
o Plants protect themselves from being eaten
• Chemical toxins, spines, thorns,

Front 17

• Parasitism

Back 17

o (+/-) interaction
o when the parasite derives its nourishment from the host

Front 18

• Endoparasites

Back 18

parasites that live in the body of the host (like tapeworms)

Front 19

• Ectoparasites

Back 19

parasites that feed on the external surface of the host (like lice)

Front 20

• Parasitoidism

Back 20

→ when insects lay eggs on the living hosts. The larvae then feed on the body of the host

Front 21

• Disease

Back 21

o Pathogens→ disease causing agents
o (+/-) relationship
o bacteria, viruses, protists, fungi, prions
o most pathogens inflict lethal harm
o pathogens can limit populations by killing off a lot of organisms

Front 22

• Mutualism

Back 22

o (+/+) interaction
o Ex: cleaner shrimp eat out of fishes’ mouths
o Ex: Plants make fruit and animals eat the fruit to spread the seeds

Front 23

• Commensalism

Back 23

o (+/0) interaction
o ex: clownfish and anemone
o ex: barnacles that grow on whales

Front 24

• Coevolution

Back 24

→ reciprocal evolutionary adaptations of two interacting species
o A change in one species acts as a selective force on another species whose adaptation in turn acts as a selective force on the first species

Front 25

• Species diversity

Back 25

o Variety of different kinds of organisms that make up a community
o Has two components→ species richness (number of different species) and relative abundance (proportion each species represents of the total individuals in the community)
o A community with a lot of different species that are equally proportioned is very diverse

Front 26

• Trophic structure

Back 26

o Feeding relationships between organisms

Front 27

• Food chain

Back 27

o Transfer of food energy up the trophic levels in an ecosystem
o Food chains within a food web are usually only a few links long
• Dynamic stability hypothesis and energetic hypothesis

Front 28

• Food webs

Back 28

o Compilation of multiple food chains

Front 29

• Energetic hypothesis

Back 29

o Explains why food chains are so short
o The length of a food chain is limited by the inefficiency of energy transfer along the chain (you lose energy as you go up the chain)
o Food chains should be longer in habitats with more plants because the starting amount of energy is greater
o That’s why food chains in Antarctica are pretty short

Front 30

• Dynamic stability hypothesis

Back 30

o Explains why food chains are so short
o Long food chains are less stable
o Population fluctuations at lower trophic levels are magnified at higher levels which can potentially cause the local extinction of top predators
o In variable environments, top predators must recover from environmental shocks (like extreme winters) that can reduce the food supply
• It’s beneficial to have a short food chain to protect higher predators
• The longer the food chain, the slower the recovery from environmental shocks for top predators

Front 31

• Dominant species

Back 31

o Species in a community that are the most abundant (have the most biomass, total mass of all individuals in a population)
o Dominant species have a powerful influence on the occurrence and distribution of other species
o Why do some species become dominant?
• Dominant species are most competitive in exploiting limited resources
• Dominant species are most successful at avoiding predation or impact of disease
• Explains why invasive species can attain high biomass in new environments
o When you remove the dominant species you realize how important it is to the environment

Front 32

• Keystone species

Back 32

o Not necessarily abundant
o Exert strong control on community structures not b/c they’re the most abundant, but because they’re important
o They have pivotal ecological roles and niches

Front 33

• Foundation species

Back 33

o Species that exert their influence on the environment by physically changing the environment
o Ex: beavers build dams and dramatically alter the physical landscape of the environment

Front 34

• Bottom up model

Back 34

o Lower trophic levels influence higher trophic levels
o ex: the number of plants influences the number of herbivores
o to change the community structure of a bottom up community you need to alter the biomass at the lower trophic levels
o removing plants would decrease herbivores which would decrease predators

Front 35

• Top down model

Back 35

o Higher trophic levels influence lower trophic levels
o Predation controls community organization
o Removing predators would increase herbivores which would decrease plants

Front 36

• Biomanipulation

Back 36

o Changing trophic structures and population numbers to change an environment
o Ex: getting rid of predators (fish) in a lake will increase zooplankton which will decrease algae which will clean up the lake

Front 37

• Nonequilibrium model

Back 37

o Communities are always changing, there’s no such thing as stability
o Communities constantly change after being disturbed by disturbances
o Disturbance→ event like a storm, fire, flood, drought, human activity
• Changes a community, removes organisms from it, alters resource availability

Front 38

• Intermediate disturbance hypothesis

Back 38

o Moderate levels of disturbance are good- they foster greater species diversity
o Ex: some pine trees require forest fires to spread their seeds and regenerate
• Pine trees in Yellowstone are adapted to recover rapidly from severe forest fires

Front 39

• Ecological succession

Back 39

o When a disturbance happens, a new variety of species colonizes and replaces the old variety of species
o New species replace old species after disturbances

Front 40

• Primary succession

Back 40

o When ecological succession happens in virtually lifeless areas
o Ex: lichen and moss colonize a barren volcanic island
o Producing a community through primary succession takes a really long time

Front 41

• Secondary succession

Back 41

o Occurs when an existing community has been cleared by some disturbance that leaves the soil intact (like after a forest fire)
o When an area is re colonized after a disturbance

Front 42

• Three processes that link early and late arriving species

Back 42

o Early arrivals facilitate the appearance of the later species by making the environment more favorable (like increasing the soil fertility)
o Early species inhabit establishment of later species
o Later species tolerate earlier species- the two don’t have a connection

Front 43

o Equatorial polar gradients

Back 43

• Tropical habitats support more species than temperate/polar regions
• Since tropical habitats are older than temperate/polar habitats, they had more time to evolve and speciate and become diverse
• Growing season in tropical forests is five times longer than other growing seasons
• More time for speciation
• Tropical habitats have ideal climate
• Have a higher rate of actual and potential evapotranspiration

Front 44

• Evapotranspiration

Back 44

o Evaporation of water from soil plus the transpiration of water from plants
o Total amount of available water
o Species richness of plants and animals correlates with measures of evapotranspiration

Front 45

• Actual evapotranspiration

Back 45

o Amount of solar radiation, temperature, and water availability
o Higher in tropical hot climates

Front 46

• Potential evapotranspiration

Back 46

o Measure of energy availability but not water availability
o Determined by amount of solar radiation, temperature
o Highest in regions with a lot of solar radiation and temp. (tropical rainforests)

Front 47

• Species Area Curve

Back 47

o The larger the geographic area of a community, the greater the number of species

Front 48

• Island Equilibrium Model

Back 48

o Island→ any area surrounded by an environment not suitable for the “island” species (doesn’t have to be an oceanic island)
o An equilibrium will eventually be reached where the rate of species immigration equals the rate of species extinction
• Number of species at this equilibrium point is correlated with the island’s size and distance from the mainland
• Small islands that are far away from the mainland have high extinction rates
• Bigger islands tend to be more diverse b/c they have more diverse resources

Front 49

• Integrated hypothesis of community structure

Back 49

o A community is an assemblage of closely linked species locked into association by mandatory biotic interactions that cause the community to function as an integrated unit
o Ex: certain species of plant are constantly found together
o Focuses on studying groups of species

Front 50

• Individualistic Hypothesis of community structure

Back 50

o A plant community is a chance assemblage of species found in the same area because they have similar abiotic requirements
o Focuses on studying individual species

Front 51

• Rivet model

Back 51

o Most of the species in a community are associated tightly with particular other species in a web of life
o Reducing/increasing the abundance of one species in a community affects many other species
o Contradicts the individualistic hypothesis

Front 52

• Redundancy model

Back 52

o Most of the species in a community are not tightly associated with one another and the web of life is very loose
o Increase or decrease in one species in a community has little effect on the other species
o Species operate independently of one another
o Focuses on individual species