Transcript 1. Explain the relationship between species

Chapter 53 Reading Quiz
1.
2.
3.
4.
5.
A bunch of populations living close
together and possibly interacting is called
a ____.
Which type of interspecific interaction is
beneficial to both species?
“Cryptic coloration” is also known as…
The links in a food chain are also called
____ levels.
The sum weight of all individuals in a
population is known as the …
1. Explain the relationship between species
richness, relative abundance, and diversity.
• Species diversity  the number and
relative abundance of species in a biological
community
• Species richness  the number of species
in a community
• Relative abundance  a measure of the
proportion of a species in the community as
a whole 
2. Distinguish between the “individualistic
hypothesis” and the “interactive hypothesis”.
• The individualistic hypothesis depicted a
community as a chance assemblage of
species found in an area because they have
similar abiotic requirements
• The interactive hypothesis saw each
community as an assemblage of closely
linked species having mandatory biotic
interactions that cause the community to
function as an integrated unit 
3. Explain how interspecific competition may
affect community structure.
• Interspecific interactions are those that
occur between populations of different
species living together within a community
• Competition will result in one species being
dominant over the other
• “Niches” come into play, and only one
species may occupy a niche; the other must
adapt to a different niche or not survive 
4. What is coevolution?
• Coevolution  a
change in one species
that acts as a
selective force on
another species
- counteradaptation
of the second species,
in turn, affects
selection of individuals
in the first species 
5. Describe the variations of predation and
parasitism.
• Can have positive,
negative, or neutral
effects on the species
involved
• Predation and
parasitism are both
(+/-) interactions
• Predation
• Parasitism
• Parasitoidism
• Herbivory 
6. What are some defenses that animals and
plants have against being eaten?
• Plants:
- thorns, spines, hooks
- chemicals, hormone analogues
• Animals:
- passive, active, mechanical, or chemical
- cryptic coloration, shape
- aposematic coloration (bright warning)
- mimicry 
7. Describe the competitive exclusion
principle, what niches are, and the evidence
that competition exists in nature.
• The competitive exclusion principle predicts that
two different species competing for the same
limiting resources cannot coexist in the same
community
- one will use resources more efficiently, thus
reproducing more rapidly and eliminating the inferior
competitor
• An ecological niche is the sum total of an organism’s
use of biotic and abiotic resources in it’s
environment
- how it “fits into” an ecosystem
• The weaker organism will become extinct OR
• One of the species will evolve to the point of using a
different set of resources 
8. Distinguish between commensalism and
mutualism.
• Commensalism is a (+/0) interaction in
which the symbiont benefits and the host
is unaffected
ex: cowbirds & cattle; sharks & remoras
• Mutualism is a (+/+) interaction requiring
the evolution of adaptations in both
species
ex: flowers & insects; lichen 
9. How do predators, mutualism, and
parasitism alter community structure?
• Predators can alter community structure
by moderating competition among prey
species (Ex: zebras & lions)
• Mutualism can have community-wide
effects (Ex: mycorrhizae fungi)
• Parasitic diseases that reduce populations
of one species also impact other species 
10. Explain how disturbance is one of the
most prominent features of most
communities.
• Disturbances are events that disrupt
communities
- they change resource availability and
create opportunities for new species
- the impact depends on the size,
frequency, and severity of the disturbance
- can be caused by natural disasters,
overgrazing by animals, alteration on
natural ecosystems 
11. Why do we consider humans to be the
most widespread agents of disturbance?
• Logging and clearing for farmland has
reduced and disconnected forests
• Agricultural development disrupts
grasslands
• Centuries of overgrazing by animals has
contributed to the famine in parts of
Africa
• Human disturbances usually reduce
biodiversity 
12. Describe the stages of succession.
• Primary succession  when life begins in
areas essentially barren due to lack of
formed soil
- volcanoes, retreated glaciers
• Secondary succession  if an existing
community has already been cleared by
some disturbance that leaves the soil
intact 
13. What accounts for the geographical
ranges of species?
• Biogeography  the study of the past and
present distribution of individual species and
entire communities
• Limitation of a species to a particular range may
be due to:
- failure of the species to disperse beyond its
current range
- failure of pioneer individuals that spread beyond
the observed range
- the species having retracted from a once larger
range to its current boundaries 
14. Describe island biogeography.
• Islands provide opportunities to study factors
affecting species diversity of communities due to
their isolation and limited size
• # of species determined by immigration and
emigration, which are determined by island size
and distance from mainland
• Smaller islands have higher extinction rates
• The farther away an island is from mainland, the
less species, relative to island size 