chapter 41 - ecological communities

Question 1

interspecific interactions

Answer 1

-organisms’ interactions with individuals of other species in the community

Question 2

competition interaction

Answer 2

-minus/minus interaction
-competition for resources that limits the survival and reproduction of both individuals

Question 3

competitive exclusion

Answer 3

-species who compete for the same limiting resources cannot coexist permanently in the same place
-one species uses resources more efficiently and reproduce more rapidly than the other
-reproductive advantage of one organism eventually leads to local elimination of the other competitor

Question 4

ecological niche

Answer 4

-the specific set of biotic and abiotic resources that an organism uses in its environment
-can use it to restate competitive exclusion
-competition for resources can cause evolutionary change in populations: evolution by natural selection can result in one of the species using a different set of resources or similar resources at a different time

Question 5

competitive exclusion restated

Answer 5

-two species cannot compete for the same limiting resources if they share the same niche

Question 6

resource partitioning

Answer 6

-the differentiation of niches that enables similar species to coexist in a species
-explains how one species can exist within the same ecological community without pushing another to extinction through competition

Question 7

fundamental niche

Answer 7

-the niche a species could potentially occupy
-competition with other species can cause one species from fully occupying its fundamental niche

Question 8

realized niche

Answer 8

-the niche a species actually occupies
-after interactions with other species has been taken into account
-what a species is driven into due to competition

Question 9

character displacement

Answer 9

-the tendency for characteristics to diverge more in sympatric than allopatric species
-sympatric species that compete for resources show differences in body structure and in the resources they use
-closely related species whose populations are sometimes allopatric (geographically separate) and some-times sympatric (geographically overlapping) provide additional evidence for the importance of competition in structuring communities

Question 10

exploitation

Answer 10

-minus/plus interaction
-individuals of one species benefits by feeding on and harming individuals of another species
-includes predation, herbivory, and parasitism

Question 11

predation

Answer 11

-predator of one species kills prey of other species
-predator adaptations: acute senses, fangs+claws+poison, fast anda agile
-prey adaptations: cryptic coloration, aposematic/warning coloration, batesian mimicry

Question 12

herbivory

Answer 12

-herbivore eats part of plant/alga (harming but usually not killing)
-herbivore adaptations: chemical sensory systems, sense of smell for plant examination, specialized teeth or digestive system
-plant adaptations: (can’t run away like animals, obviously) chemical toxins or structures (spines or thorns)

Question 13

parasitism

Answer 13

-parasite derives nourishment from and thus host
-parasite adaptations: endoparasites live within host’s body, ectoparasite feed on host’s external surface, complex life cycles, change host’s behavior

Question 14

positive interactions

Answer 14

-at least one individual benefits and neither are harmed
-large effects on ecological communities
-includes mutualism and commensalism

Question 15

mutualism

Answer 15

-members of both species benefits
-common in nature
-while there may be costs involved in some interactions, the benefits outweigh these costs

Question 16

commensalism

Answer 16

-individual of one species benefits and the other neither benefits nor is harmed
-also common in nature

Question 17

species diversity (of a community)

Answer 17

-the variety of different kinds of organisms that make up the community
-a few species can exert strong control on a community’s structure, including number and relative abundance of the species
-two major components: (1) species richness, (2) relative abundance

Question 18

relative abundance

Answer 18

-component of species diversity
-the proportion each species represents of all individuals in a community

Question 19

species richness

Answer 19

-component of species diversity
-the number of different species in the community

Question 20

biomass

Answer 20

-the total mass of all organisms in a habitat

Question 21

-introduced species

Answer 21

-organisms that humans have moved to regions outside of the species’ native range
-more diverse communities are more resistant to introduced species because these diverse communities capture more resources available in the system, leaving fewer for the introduced species

Question 22

trophic structure

Answer 22

-the feeding relationships between organisms
-also (in addition to species diversity) what the structure and dynamics of a community depends on
-trophic interactions of a species have a large impact on the structure of entire communities

Question 23

food chain

Answer 23

-transfer of food energy from its source in plants and autotrophs/primary producers through herbivores/primary consumers to carnivores/secondary/tertiary/quaternary consumers and eventually to decomposers

Question 24

trophic level

Answer 24

the position an organism occupies in a food chain

Question 25

food web

Answer 25

-a group of food chains linked together
-food chains are not isolated units that are separate from other feeding relationships in a community

Question 26

foundation species

Answer 26

-have strong effects on their communities as a result of their large size/high abundance
e.g. trees, desert shrubs, marine algae
-community-wide effects because they provide a habitat or food
-may be competitively dominant: superior in exploiting key resources

Question 27

keystone species

Answer 27

-not usually abundance in a community
-exert strong control on community structure by ecological role, not their numbers

Question 28

ecosystem engineers

Answer 28

-species that create or dramatically alter their environment
-can modify the physical environment in ways that create habitats on which other species depend

Question 29

bottom-up model

Answer 29

-model of community organization
-unidirectional influence from lower to higher trophic levels
-to change community structure of a bottom-up community, biomass needs to be altered at lower trophic levels to allow those changes to propagate up
-e.g. adding mineral nutrients –> plant growth –> higher trophic levels increase in biomass

Question 30

top-down model

Answer 30

-model of community organization
-predation mainly controls community organization because predators limit herbivores, herbivores limit plants, and plants limit nutrient levels through nutrient uptake
-alternating effects throughout this model
-can be seen in biomanipulation

Question 31

biomanipulation

Answer 31

-attempt to improve water quality in lakes with high abundance in algae
-alters density of higher-level consumers

Question 32

disturbance

Answer 32

-influences species diversity and composition
-an event, such as a storm, fire, flood, drought, or human activity
-changes a community by removing organisms from it or altering resource availability

Question 33

nonequilibrium model

Answer 33

-emphasis on change in communities
-most communities are constantly changing after disturbance

Question 34

intermediate disturbance hypothesis

Answer 34

-moderate levels of disturbance foster greater species diversity than do high or low levels of disturbance
-high levels of disturbance reduce diversity by creating environmental stresses that exceed the tolerances of many species
-low levels of disturbance can reduce species diversity by allowing competitively dominant species to exclude less competitive ones
-intermediate disturbances foster greater species diversity by opening up habitats for occupation by less competitive species –> rarely create conditions so severe that they exceed the environmental tolerances or recovery rates of potential community members

Question 35

ecological succession

Answer 35

-a disturbed area may be colonized by a variety of species, which are gradually replaced by other species, and so on

Question 36

primary sucession

Answer 36

-ecological succession begins in virtually lifeless area
-typically the only life forms are protists and prokaryotes

Question 37

secondary succession

Answer 37

-recolonization of an area after a major disturbance has removed most but not all of the organisms in a community

Question 38

evapotranspiration

Answer 38

-the evaporation of water from soil and plants

Question 39

species-area curve

Answer 39

-all other factors being equal, the larger geographic area of a community, the more species it has because larger areas offer a greater diversity of habitats

Question 40

pathogens

Answer 40

-disease-causing microorganisms and viruses
-produce clear effects on community structure

Question 41

zoonotic pathogens

Answer 41

-pathogens that are transferred to humans from other animals