Download Chapter 41 Reading Guide: Species Interactions

Chapter 41 Reading Guide: Species Interactions
41.1 Interactions within a community may help harm, of have no effect on the
species involved
Define the following terms…
Community: A close group of populations of different species living close enough to interact
Interspecific Interactions: Interactions with individuals of other species in the community
Interspecific competition: a -/- interaction in which individuals of different species compete for a resource that limits
their growth and survival.
Competitive exclusion: two species competing for limited resources coexist; one will use the resources better and
reproduce more rapidly
Ecological Niche: the specific set of biotic and abiotic resources that an organism uses in its environment
Resource partitioning: The differentiation of niches that enable similar species to coexist in a community.
Character displacement: The tendency for characteristics to diverge more in sympatric that allopatric populations of
two species.
Predation: a +/- interaction between species in which one species (predator) kills and eats the prey.
Herbivory: a +/- interaction where an organism eats parts of plant or algae
Symbiosis: a relationship when two or more species live in direct and intimate contact with one another
Parasitism: a =/- symbiotic interaction when the parasite derives nourishment from its host that is harmed in the
process
Mutualism: an interspecific interaction that benefits both species (+/+)
Commensalism: an interaction between species that benefits one of the species but neither harms nor helps the other
(+/0)
Facilitation:
thatof
have
positive effects
(+/+ or 0/+) on the survival and reproduction of other species without
List fivespecies
examples
Interspecific
Interactions
directly living in intimate contact of a symbiosis.
Competition predation herbivory, symbiosis, and facilitation
Describe how the symbols + and – are used to indicate interactions
It describes the survival of each species, for example predation is a +/- interaction, with a positive
effect for those that hunt, negative for those being eaten.
What was Gause’s experiment and what did he conclude?
He cultured two species (separately) under stable conditions and added food each day. Both
grew and leveled off at carrying capacity. But when put together, one became extinct and one
thrived. He concluded two species competing for limited resources cannot permanently coexist in
the same place.
Explain the connection between a species fundamental niche vs. its realized niche.
Fundamental is the niche potentially occupied by that species. While the realized niche is the
portion of its fundamental niche that it actually occupies in a particular environment.
Explain the difference between allopatric populations (geographically separate) and sympatric
populations (geographically overlapping).
Allopatric populations of species tend to be morphologically similar and use similar resources,
while sympatric populations would compete for the same resources they use.
What are some examples of morphological and physical defense adaptations that prey develop?
Some examples are: Cryptic Coloration (camouflage), aposematic coloration (a chemical defense
that exhibits a warning color, like that of the poison dart frog), Batesian mimicry (a harmless
species mimics a harmful one), Mullerian mimicry (two or more unpalatable species resemble
each other. Ex: a cuckoo bee and a yellow jacket).
What adaptations do herbivores have that allow them to survive the way they do?
Some have chemical sensors at their feet that enable them to distinguish if a plant is toxic or
nutritious. Some have a sense of smell that allows them to examine plants. A lot have specialized teeth
or digestive systems that allow them to process as a vegetarian.
Why do changes in either species of mutualism affect the survival and reproduction of the other?
Due to the coevolution of related adaptations in bother species.
41.2 Diversity and tropic structure characterize biological communities
Define the following terms…
Species Diversity: The variety of organisms in a community
Species Richness: the number of different species in the community
Relative Abundance: the proportion each species represents of all individuals in the community
Biomass: total mass of all individuals in a population
Invasive Species: organisms that become established outside their native range and have the potential to seriously harm an
ecosystem
Tropic Structure: the feeding relationships between organisms in the different tropic levels, may also be referred to as the food
chain
Bottom-up Model: V-> H, here the presence or absence of mineral nutrients controls plant numbers (V), which in turn
controls herbivore numbers (H), which then controls predator numbers (P). To change community structure, you must
alter biomass at the lower trophic levels, changing predator numbers will not extend to lower levels.
Top down Model: (N <- V <- H <- P) opposite of bottom-up, here predator numbers control biomass of lower trophic
levels
Biomanipulation: using the top down model to increase water quality in polluted lakes.
What are the components of species diversity?
Species richness and relative abundance
Explain the Shannon Diversity index. Write the equation, meanings of each variable and it’s use.
This equation calculates the index of diversity using species richness and relative abundance. A
higher Shannon Diversity (H) value indicated a more diverse community.
𝐻 = −(𝑝𝐴 ln 𝑝𝐴 + 𝑝𝐵 ln 𝑝𝐵 + 𝑝𝐶 ln 𝑝𝐶 … )
A,B and C are the species in the community and p is the relative abundance of each species.
What are the five advantages to having a more diverse community?
More diverse communities are generally more productive, can better withstand and recover from
environmental stress and are more stable. They are also more resistant to invasive species.
Explain trophic structure in terms of primary producers, primary consumers, secondary consumers,
tertiary consumers and quaternary consumers (you may make a diagram if that’s helpful to you)
The transfer of food energy from its beginning source in pants and other autotrophs (primary
producers) through herbivores (primary consumers), to carnivores (secondary, tertiary and
quaternary consumers)
Draw an example of a food web
How do Dominant, Keystone species and ecosystem engineers impact their community?
Dominant: the most abundant species in a community, making them have a high amount of
tropic interactions
Keystone: Although not abundant in a community, these species have pivotal ecological roles or
niche Ecosystem engineers: dramatically alter physical environment, such as be
41.3 Disturbance influences species diversity and composition
Define the following terms….
Disturbance: an event, such as a storm, fire, drought, or human activity, that changes a community by
removing organisms or altering resource availability.
High level disturbance: result of frequent and intense disturbance
Intermediate disturbance hypothesis: moderate levels of disturbance foster greater species diversity than do
high or low levels of diversity
Ecological succession: A bare disturbed area may be colonized by one species, which is gradually replaced by
another species, which is replaced by another species…..
Primary succession: ecological succession that begins in a lifeless areas where soil has not yet been formed.
Only life forms initially present are prokaryotes and protists then lichens and mosses are commonly the first
colonizers.
Secondary succession: ecological succession that begins in an area that’s been wiped out by a disturbance that
leaves soil intact
Compare the “balance of nature” view to the nonequilibrium model.
Balance of nature: The view that biological systems are at equilibrium unless seriously disturbed
by human activities. They were stable, or have a relatively constant composition of species.
Nonequilibrium: current model of thinking, describes most communities as constantly changing
after disturbance
How is an intermediate level of disturbance good for species diversity?
High levels of disturbance create high levels of stresses so that certain species may not survive.
Low levels of disturbance allow competitively dominant species to exclude less competitive ones.
But moderate levels of disturbance open up habitats for less competitive species.
How can large disturbances be important for an ecosystem?
Some ecosystems are dependent on large disturbances. The pinecones of trees in Yellowstone do
not open unless exposed to the intense heat of forest fires.
Describe the process of primary succession.
Only life forms initially present are prokaryotes and protists then lichens and mosses are
commonly the first colonizers. Soil develops gradually and then lichens and moss are overgrown
by grasses, shrubs and trees. Then its colonized by plants that become the primary vegetation.
This may take hundreds of thousands of years.
Describe the three possible links between early and late arriving species.



Early arrivals may facilitate the appearance of later species by making the environment
more favorable
Early species may inhibit that arrival of later species so that colonization happens in spite
of the actions of early species
Later species tolerate the independent actions of the initial species
41.4 Biogeographic Factors affect community diversity
Define the following termsEvapotranspiration: the evaporation of water from soil and plants together (a function of solar radiation temperature, and
water availability is higher in hot areas with abundant rainfall)
Potential evapotranspiration: a measure of water loss that assumes that water is readily available (determined by amount of
solar radiation and temperature and is highest in regions where both are plentiful.
Island Equilibrium model: The idea that an equilibrium on an island will eventually be reached where rate of species extinction
equals immigration.
What are two biogeographical features in particular that contribute to the range of diversity in a
community?
The latitude of a community, and the area it occupies.
What did Darwin and Wallace point out that was later confirmed by current researchers?
Plant and animal life was more generally abundant and diverse in the tropics than other parts of
the globe
What are the two key factors affecting latitudinal gradients of a species?
Evolutionary history and climate
Why is species diversity greater in tropical regions than in temperate Polar Regions?
Because of their longer evolutionary history and the greater solar energy input and water
availability in tropical regions.
Explain the species-area curve
All other factors being equal, the larger geographical area of a community the more species it
has.
What are two factors that determine the number of species on the island?
The rate at which new species immigrate to the island and rate at which species become extinct
Explain the relationship between total species and extinction and immigration rate on an island.
As the number of species on the island increases, immigration decreases because any individual
reaching the island is less likely to represent a species not already present. Extinction rates
increase as well because of the greater likely hood of competitive exclusion.
What are two physical features on an island that affect immigration and extinction rates?
Size (smaller islands generally have lower immigration rates because potential colonizers are less
likely to reach a small one than a larger one), and distance from the mainland (closer island will
have more immigration rates)
41.5 Pathogens alter community structure locally and globally
Define the following termsPathogens: disease causing organisms and viruses
Zoonotic pathogens: those that are transferred from humans to other animals
How are zoonotic pathogens transferred?
Through direct contact with an infected animal or by means of an intermediate species called a
vector (parasites including ticks, lice, or mosquitos)
Give an example of how pathogens can affect the structure of a community
In the forests and savannas of California, trees of several species are dying from sudden oak
death.