Ecology –Test Review Chapter 2 (History of Ecology & Evolution & Natural Selection)
1. Defintion of Ecology (technical definition):
Study of inter-relationships between organisms and their environment
2. Ecology's Greek translation:
Study of the home
History
1. Know the contribution of each of the following personalities from ecology's brief history:
Haeckel
Darwin
Mendel
Malthus—see #3 below
First to use term
theory of evolution by
father of genetics,
ecology
natural selection
demonstrated the role of genes in producing variation
2. List the 2 most important events or milestones in the History of Ecology.
a. Darwin’s publishing of “Origin of Species”, explaining his theory of evolution by natural
selection
b. The Environmental Movement of the 1960’s and 70’s---degradation of the earth’s ecosystems reached critical levels. People became aware of how rapidly a growing human
population was changing the earth and established laws and programs to solve environmental problems
3. What idea did Darwin "steal" from Thomas Malthus when he (Darwin) created his theory of
evolution by natural selection ?
Malthus wrote a short paper describing the problems human population would encounter
as a result of exponential growth. He predicted humankind would outgrow the earth’s ability
to provide needed resources---Darwin believed only the fittest would survive such conditions
4. Why are Darwin's theories regarding natural selection and evolution important to the science
of ecology?
Darwin’s natural selection credits forces in the environment for causing species to evolve or
change. Since ecology focuses on the environment around organisms, Darwin’s theory gives
credibility to the science of ecology and helps us better understand concepts within ecology.
5. If the environment has always been changing, why are the environmental changes seen in the
1960's and 70's considered so much more important? Recent changes are more and more of
human action and are occurring too rapidly and too widespread for some organisms—they
may not be able to adapt fast enough to survive. Thus we have numerous endangered species
today.
Natural Selection and Evolution
1. Explain how organisms evolve or change (adapt) through natural selection.
Evolution by natural selection is a process in which a species produces a variety of offspring.
These offspring face a host of forces (disease, predators, pollution, weather, etc.) in the
environment that act to “select” which organisms survive and which do not. These forces favor
some of the variety of organisms over others and thus drive the direction of change in a species.
2. How does the peppered moth example from 19th century England demonstrate
evolution by natural selection? (recall our lab simulation or see text p.41)
In the early 1800’s white peppered moths far outnumbered the melanistic black form in an
Environment in which being white was favored and thus selected for. As the Industrial
Revolution progressed through the middle of the 1800’s, southern England became polluted by
air-borne particulates originating from the burning of coal. This “new” environment favored
the black variety of peppered moth and selected against the white variety. In a matter of decades
the peppered moth population of southern England changed from predominantly white to
predominantly black---it evolved under the natural selection forces created by a coal polluted
landscape.
3.
How do we know when an adaptation is a positive one for an organism? What's the best test?
When an organism survives long enough to reproduce, its adaptations are deemed successful
and the organism is considered “ecologically fit”.
4.
For a species to adapt and evolve under natural selection forces, they must be able to produce
__variation_in their offspring, but this depends on the population numbers being relatively
large.
5.
What are the 2 sources of genetic variation in a population?
a. Sexual reproduction—critical in most animals and higher plants
b. Mutations—mistakes in the DNA code or chromosomes, especially critical to simple organisms
that can only reproduce asexually, such as bacteria and other microbes
6. Explain the benefits of genetic mutations (ecologically).
Mutations create change in an organism’s genetic code, producing variations in organisms
that may, in the right environment, make the organism more fit to survive.
7. When populations become too small, they are less likely to adapt to environmental change. How
come ? Small populations have smaller gene pools—less variety and may see an increase in
in the number of deleterious gene combinations that result in less fit offspring.
8. Small populations may experience either genetic drift or inbreeding. Be able to define each of
these. Genetic drift is a radical shift or change in a gene pool, often resulting when a small
population is isolated and lacks genetic variety---mating remains random (not between kin)
during genetic drift. Inbreeding, on the other hand, results when small populations are
so low in number that reproduction between kin occurs—this is often necessary to sustain
any reproduction at all.
Although slightly different by definition, g. drift and inbreeding have a similar effect on the gene
pool or genetic make-up of a population. Explain. Both reduce variation and increase the odds
that deleterious (negative) gene combinations arise—reducing the fitness of the population’s
individuals.
9. Small populations are affected genetically in three major ways. What are they?
(One is given---give the other two.)
a. Loss of genetic variation
b. Increased risk of deleterious gene combinations
c.
Loss of “heterozygosity” in the gene pool
10. At what rate (percentage-wise) does inbreeding occur in natural populations? Less than 1 %
11. Explain how the concepts of genetic drift and inbreeding are related to the topic of Endangered
Species??? Populations that are endangered have reduced numbers—seriously endangered
species that drop to levels that approach minimum viability (50-500)no doubt begin to genetically
drift as they become isolated in smaller and smaller fragments of the population---they lose
variation and become less and less fit as deleterious gene combinations arise and the potential
for inbreeding with kin goes up. Ultimately, a population’s own genetics and the lack of
genetic variation become its worst enemy in the struggle to avoid extinction.
12. Give the generally accepted value for minimum viable population size._50_to__500___.
What does minimum viable population mean? Minimum viable population is the minimum
size a population can sustain and still have some hope of avoiding extinction---think of it
as the lowest you can go and still have any hope of survival. Once a population dips below
50, the odds of its survival are very, very low---extinction is imminent.
13. What is co-evolution? Co-evolution occurs when two species evolve in response to one another
--each acting as somewhat of a natural selection force driving the evolution of the other
Give some examples:
As an owl species develops quieter flight a mouse population develops better hearing
14. How does our lab with "light" and "heavy" hares (white and brown bean simulation lab)
demonstrate the role of natural selection in the evolution of a species ?? Recall that when natural
selection favored the white beans and selected against brown, the population changed or evolved
a predominantly white population, but when we removed natural selection forces, evolution
stopped—the ratio of white to browns remained more or less the same—the population was
not changing because there was no natural selection to drive or force the change.
15. What options are available to assist the survival of endangered species that have reached
population level that are deemed “minimum viable” ??? Captively breed the population in
zoos, etc., introduce new individuals, if available, from other populations to increase variety
in the gene pool, protective laws to reduce hunting and other harvesting of the species,
preserve and increase available habitat for the species
16. In the choices below, circle the descriptions of structural adaptations and underline descriptions
of behavioral adaptations.
a. A colony of beavers builds a dam to slow the flow of water and create a pond in which to
build its “lodge”.
b. A snake crawls atop a rock pile to “sun” itself on a warm, clear summer day.
c. A bald eagle develops white head and tail feathers as it approaches adulthood at age four or
five.
d. A wolf howls to communicate with other members of its pack.
e. A male cardinal sings at various locations within its habitat to establish the boundaries of its
nesting territory.
f. The feet of many species of ducks are webbed to enhance the birds’ abilities to swim.
17. In the choices below, circle the descriptions of phenotypic plasticity and underline descriptions
of evolution.
a. A bacteria population grows resistant to antibiotics after infecting a host population over
several years.
b. A short-tailed weasel sheds a coat of brown fur in late fall, slowly replacing its “pelage”
with white hair.
c. A minnow taken from darkly stained water and held in captivity in clear, brightly lit water
becomes noticeably lighter in color.
d. Today’s cheetahs are slightly faster than cheetah populations that existed two or three
decades ago.
18. Small Population Terminology MATCHING PRACTICE:
C
____Genetic Drift
A
____Founder Effect
B
____Inbreeding
19. What are the 5 Steps in Darwinian Evolution ?
(guaranteed to be one of the essays you must write on the test)
a. Overproduce offspring
b. Off spring face a struggle to survive numerous natural selection forces
c. Organisms produce variation in their offspring
d. The fittest organisms survive—survival of the fittest
e. The fit survive and reproduce, starting the entire cycle or evolutionary process
20. Why is it crucial that a population continues to produce a variety of offspring generation after
generation ? A continuing variety of offspring helps increase the chances that some will
no matter what changes might occur in the environment in the future---since environmental
changes are unpredictable, the only way a species can hope survive is to keep producing
variation and hope that some varieties are fit for the environments they encounter
21. What exactly is natural selection and how does it drive the direction evolution takes ?
Natural selection is the sum total of forces in the environment that act to select in favor of
organisms survival, while selecting against the survival of other individuals—it acts
to direct the path of evolution a species will take
22.What are the only two significant means by which living things can create variety in their
offspring ? Answered before—sexual reproduction and mutation