Biology 1 Chapter 20

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Transcript Biology 1 Chapter 20

Community Ecology
The main predators of field mice in a certain
ecosystem are rattlesnakes and foxes. Suppose
humans begin building neighborhoods in the
ecosystem, driving out many of the indigenous
rattlesnakes and foxes. What will most likely happen
to the field mice's population?
A. The population will not be affected by the change.
B. The population will decrease in size.
C. The population will increase in size.
D. The population will occupy an entirely new niche.
Answer: C
Predation-an individual of one species, the
predator, eats all or part of an individual of
another species, the prey.
Carnivores-predators that eat animals
Herbivores-predators that eat plants.
All heterotrophs are either predators or
parasites or both.
Produce toxins
Mimicry-one species closely resembles
another species
Batesian mimicry-harmless species
resembles venomous species
 Ex. Harmless king snake & venomous coral snake
Mullerian mimicry-two or more dangerous or
distatesful species look similar
 Ex. Bees and wasps
Physical defenses
 Thorns, spines, sticky hairs, tough leaves
Chemical defenses
 Secondary compounds-chemicals that are
byproducts of the plants’ metabolism and are
harmful or distasteful to animals.
Intraspecific competition-interactions
between members of the same species
competing for the same resources.
Interspecific competition-a type of
interaction in which two or more species use
the same limited resources.
 Ex. Lions & hyenas compete for zebras
Competitive Exclusion-one species is
eliminated from a community because of a
competition for the same limited resource.
Niche-the role that the species plays in its
Fundamental niche-the range of conditions
that the species can potentially tolerate
Realized niche-the part of the niche that the
species uses.
Character Displacement-the evolution of
differences in a characteristic due to
Competition is the most intense between
similar species that require the same
Resource Partitioning-similar species coexist
so that each species may avoid competition
with others by using a specific part of an
available resource.
Symbiosis-a close, long-term relationship
between two organisms
Parasitism-one individual is harmed while the
other benefits; does not usually result in the
immediate death of the host.
Host-is harmed
Ectoparasites-Remain on the outside of the
Endoparasites-Live inside the
host’s body.
Mutualism-two species derive benefit from
each other
Some mutualistic relationships are so close
that neither species can survive without the
 Ex. Pollination
Commensalism-one species benefits and the
other species is not affected.
 Ex. Species that scavenge for leftover items
 Crash Course-Intro to Ecology
The Toolache Wallaby was a kangaroo species in Australia that
became extinct in the 20th century. The wallaby was hunted by
humans, as well as animals brought to Australia by humans.
Humans also cleared the land where the wallaby lived and foraged
for food. Given this information, which of the following
environmental changes caused the Toolache Wallaby to become
 I.
 II.
 III.
 IV.
loss of habitat
climate change
introduction of non-native species
I and III only
II and IV only
I, II, III and IV
I, II, and IV only
Species richness-the number of species in the
 Varies with latitude (distance from the equator)
 Closer to the equator has more species richness.
Species evenness-the relative abundance of
each species
Species-area effect-Larger areas usually
contain more species than smaller areas do.
 Most often applied to islands, where area is
limited by geography.
Disturbances-events that change
communities, remove or destroy organisms,
or alter resource availability.
 Abiotic-drought, fire, flood, volcanic eruption,
earthquake, storms
 Biotic-elephants tearing up trees or prairie dogs
moving soil, humans bulldozing, clear-cutting,
paving, plowing, or mowing.
Stability-the tendency of a community to
maintain relatively constant conditions; a
community’s resistance to disturbances
Ecological succession-the gradual, sequential
regrowth of a community of species in an
Primary Succession-the development of a
community in an area that has not supported
life previously, such as bare rock, sand, island
formed by volcanic eruption.
Soil is not initially present.
Secondary succession-the sequential
replacement of species that follows
disruption of an existing community
Ex. Fire, storm, human activity
Pioneer Species-the species of organisms
that predominate early in succession
Tend to be small, grow quickly, and
reproduce quickly.
Climax Community-The community proceeds
through a predictable series of stages until it
reaches a stable end point.
Crash Course-Succession
Microorganisms can mutate and evolve very quickly compared to
most multicellular organisms. This allows pathogenic
microorganisms to infect new species. Suppose a very harmful
microorganism that is quite successful at infecting hardwood
trees is introduced into a forest ecosystem. What effect would
this pathogenic microorganism most likely have?
A. It would maintain the balance of the ecosystem by reducing
the populations of all the species.
 B. It would maintain the balance of the ecosystem by reducing
the population of one species.
 C. It would disrupt the ecosystem by infecting and killing the
populations of all the species.
 D. It would disrupt the ecosystem by greatly reducing the
population of a few species.
Answer: D
Mutualism and Niches
Competetive Exclusion