Download Answers to Questions 1-14 From Chapter 8 A sea otter is an

Answers to Questions 1-14 From Chapter 8
1. A sea otter is an example of a keystone species because of it’s importance in the kelp bed
ecosystem. It eats sea urchins, which in turn eat kelp, so the balance of sea urchin/kelp beds is
maintained by the presence of the otter. If the sea otter is removed from this ecosystem, the
urchins will eat up all the kelp, and the whole ecosystem collapses. By the way the sea otters
habitat and range is right here off the coast of Cali…..starting at about Monterey and all the way
up to Northern Cali. They are super awesome if you ever get to see one in nature!
2. Population ecology is basically the study of how populations within ecosystems change over
time and space in response to what is going on in the environment
3. Of course population distribution patterns change as seasons change, but generally speaking,
the three main ways that populations are distributed in nature are; uniform, clumped, and
irregular.
-Uniform distribution is when organisms are evenly spaced out throughout their habitat, usually
so that they don’t have to compete for resources. Many plants have uniform distribution, in
some cases penguins exhibit this as well.
-clumped is the most common distribution pattern, it’s when organisms (animals) clump
together so that they can kind of share and maximize the resources present, also they can care
for young together and hunt together too.
-Random distribution is usually seen in plants although it is considered rare, it happens when
the wind or water randomly carries seeds or spawn to random places and the organisms sort of
grow where they land.
4. Examples would be: Uniform-Joshua Trees in the desert, clumped-elephants in the savanna,
random=dandelions in the field
5.
6. Biotic potential is the maximum reproductive capacity of a population to reproduce if there were
nothing holding them back (lack of resources or limiting factors prevent a population from over
producing)
7. A fly would have greater biotic potential than an elephant because the fly is small, has many offspring,
has a short lifespan, and is a generalist species, also a fly does not care for its babies and is an r-selected
species, whereas an elephant has a lower biotic potential, it is large in size, has few offspring, oh and
also great parental care, long lifespan, and is k-selected.
8. Environmental resistance is what prevents an r-selected species from over taking the world,
environmental resistance is simply factors in the environment that stop a population from growing, like
a virus or a parasite, or the lack of food or space. (limiting factors)
9. Environmental resistance
10. Things like viruses, bacteria, lack of food, a natural storm or earthquake, a fire, parasites, predators
would all be examples of environmental resistance.
11. The two factors that determine carrying capacity are biotic potential and environmental resistance.
12. Exponential growth as it relates to populations refers to the rapid growth of population. It starts out
slow and then as the base of reproductive individuals increases, the population begins to rapidly
increase. This type of growth results in a “J- shaped” curve.
13. Logistic growth refers to population growth that starts out exponentially, and then as environmental
resistance “pushes” down on the population, the population growth begins to level out and slow down,
the population begins to reach it’s carrying capacity in the ecosystem. We call this an “S-shaped” curve.
14. A population dieback happens when a population is growing at an exponential rate and the
resources in the environment begin to be depleted, the population reaches it’s carrying capacity in the
ecosystem. The population then “crashes” or suffers a massive die off which we call a “dieback”. Usually
it takes time which is called “reproductive lag time” this is because it takes time for the birth rate to fall
and the death rate to rise in response to resource overconsumption.