Download Answers to Questions for 16,17 and 19

16.1 Answers:
1. * A scientific theory of evolution
* explains how modern organisms change over
time through decent from common ancestor
2. a) species vary globally
•
many locations where animals were similar
but not the same
•
animals in some locations but not in others
(ex. rabbits, kangaroo)
b) species vary locally
•
related but different animal species occupy
different habitats in a local area
(ex: Galapagos tortoises on different
islands)
c) species vary over time
•
he collected fossils and noticed that some
fossils were similar to living specimens
16.2 Answers:
3. The earth is very old. Earth is still
changing its surfaces.
•
Lyell’s book helped Darwin understand the significance
of geological change (ex: earthquake) and how over
many years, a mountain range could be made, etc.
(rocks under the sea could be pushed to surface, etc.)
*Darwin asked himself: “If earth can change so much
over time, could living things do the same?”
4. Lamarck was a naturalist. He said:
1. used body parts would get bigger,
unused parts would shrink
**Darwin wanted to know
WHY fewer organisms
3. organisms have a desire to change
survive than are created.
5. Lamarck was NOT correct.
He wanted to know WHY
some survived and some
6. Malthus said that if human population continued to grow
with more births than deaths, food and space would soon did not…ie; what was the
REASON
run out and disease, famine, war will result to limit
2. acquired characteristics are inherited
population.
16.2 Answers Continued
7. Nature provides the variation (thru mutations)
and humans SELECT those traits which are
useful.
ex: breeding animals and plants only with the
desired characteristics (think selective breeding from
last unit)
** Darwin recognized that variations were the
raw materials needed for evolution to occur
16.3 Answers (#8)
Struggle for Existence:
* after reading Malthus’ work, Darwin
realized that if there is limited food and
space for a population, that set up a
natural competition and struggle for
those resources
Variation and Adaptation:
* Darwin knew individuals varied. Some
variations may be better suited to win in
the competition for resources. This was
an advantage. “adaptation”= any
inheritable characteristic which increases
one’s ability to survive and reproduce in
an environment.
Survival of the Fittest:
* a connection between how an
organism “makes a living” and the
environment it is in.
* differences in rates of
survival/reproduction = survival of fittest.
“fitness”= how well one can survive
and reproduce in a given environment
16.3 Answers cont’d
9. Natural Selection: organisms
with best variations to survive
the given environment will
survive better, longer, and
reproduce. Now, those best fit
genes will be passed on.
Fig  protective coloration of
green variety allows more of
them to survive and reproduce.
After time, there are more green
than brown in the population
10. Natural Selection is NOT:
* geared to make one “perfect”
* purposeful
* moving in one direction
Natural Selection IS:
• a process of making one
good enough to survive a
given environment and pass
genes to next generation
** IF the environment changes, a
new selection process may begin
and a new phenotype may be
better fit to survive.
ex: What if in Fig 16-10, there
was a severe drought one
summer. What may happen?
16.3 Answers cont’d
11. Natural Selection depends on descendants to
leave genes for the next generation. Well
adapted species survive over time.
* Darwin said that over time, one species may
change enough to evolve into another
* also said that living species have descended
(with changes) from a common ancestral
species
* evidence of this is present in the fossil
record.
* from this he drew the first “evolutionary
Tree”
* all species- living and extinct- are
descended from ancient common ancestors.
* The “Tree of Life” links all living things
16.4 Answers
12. Biogeography- looking at
patterns in the distribution of living
things. Where things live now and
where their ancestors lived in the
past
** these patterns in fossils and
living specimens tell us how
modern species may have
evolved from their ancestors
a) closely related but different:
* on Galapagos, biogeography
suggested that island species
evolved from mainland species.
*Natural selection over time
maintained those best adapted to
that particular island environment.
* compared to mainland
specimens, the island ones were
closely related but different
b) distantly related but similar:
* animals and plant in similar
environments globally may
have similar adaptations due
to similar environmental
pressures.
*BUT: these animals and
plants are not closely related
*ex: ground-dwelling birds in
Europe, Australia, Asia look
different, but have developed
similar adaptations to survive
in a similar environment
separately
16.4 Answers cont’d
13. * fossils discovered after
Darwin fill in some of the
“gaps” in the evolution/fossil
record.
* one fossil shows the
evolution of whales from a
land-based mammal.
14. Homologous structures:
similar in design, different in function.
ex: bird wing, human arm, frog front leg
* shows evolutionary relationship due
to similar bone pattern and genetic info
to make it the same way
15. Analagous structures
have same function but
different design. ex: bird
wing and insect wing. do not
support common decent
16.4 Answers cont’d
16.Traces of homologous structures in other species.
ex: hip bone in dolphin are vestiges of it’s
ancestor’s pelvic bone
ex: third eye lid, appendix, tail bone
*genetically and evolutionarily links all animals
who make whole or part of that structure
17. Similar patterns in embryonic development is
evidence of decent from common ancestor
ex: human, pig, frog, fish early embryos
are all very similar
(tail and gill slits (pharyngeal pouches))
18. * Genetic Code for translation of DNA is universal
* All life uses ATP as energy molecule
* All life has it’s instructions in DNA molecule
* common proteins like cytochrome c in all living things
17.1 Answers
1. Evolution: a genotype determines a
phenotype. This phenotype may be an
advantage to the survival of that
organism.
* evolution is the CHANGE in the
frequency of alleles in the gene pool of a
population over time
2. Gene pool = all the genes (alleles) of a
species
3. relative (allele) frequency = how often the
allele is present in the gene pool – it does
not matter if the allele is dominant or
recessive.
4. CHANGE in the frequency of alleles in the
gene pool of a population over time
add: ** Natural Selection operates on
INDIVIDUALS, but the changes in allele
frequencies show up at the POPULATION level.
Q: in a total of 50 alleles, 20
are B (black) and 30 are b
(brown). How many of each
allele would be present in a
total of 100 alleles?
Q: What is the relative
frequency of the dominant
allele (B) and the recessive
allele (b)?
Q: If the relative frequency of
B allele changes to 30%, the
population is evolving
(changing)
17.1 Answers cont’d
5. 3 sources of genetic variation:
a) mutation: at level of gene or chromosome
* may or may not affect fitness of individual
* must be made in germ cells to affect offspring
b) genetic recombination in sexual reproduction:
* alignment of tetrads (metaphase) produces
8.4 million gene combinations per gamete!
* crossing over prior to this makes countless more
variations per gamete!
c) lateral gene transfer: DNA transfer to non-offspring
* bacterial plasmid swapping
6. Depends on how many genes control a trait
7. Single: a trait controlled by ONE gene, 2 or 3
phenotypes possible
ex: banding in snail shells
* phenotypic ratios determined by frequency
of alleles AND if they are dominant or
recessive (banded shell is recessive)
17.1 Answers cont’d and 17.2 Answers
8. Polygenic trait: controlled by 2+ genes, each with
2+ alleles. Therefore: many phenotypes result.
ex: human height
9. Bell-curves show distribution of a polygenic trait
17.2 Answers:
10. Natural selection on single-gene traits can lead to
allele frequency changes and therefore phenotype
changes.
ex: mutation causes red and black
body color in lizard
* red more visible…eaten quicker
* black absorb more sun, get
warmer faster, more energy to
avoid predator…
17.2 Answers cont’d
11. Effects of natural selection on polygenic traits
is more complex:
•
in bell curve distribution, fitness can vary from
one end of curve to another.
•
when fitness varies, natural selection can act.
•
can produce 3 types of selection:
a) directional: when those at ONE end of curve
have higher fitness than those at middle or other
end.
ex: large beaks needed to eat large seeds
b) stabilizing: when those at CENTER of curve
have better fitness than those at either end
ex: avg. birth weight in babies
c) disruptive: when those at EITHER end of curve
have better fitness than those at middle
ex: if medium size seeds become less common
17.2 Answers cont’d
12. Genetic Drift: when an allele becomes more
or less common by CHANCE (not nat’l sel.)
and allele frequencies show a dramatic
change
* in small populations, individuals left after a
major event don’t represent original gene pool.
* a. bottleneck effect – after a natural disaster
(disease, flood, fire, famine), the few survivors
don’t represent the original gene pool
- reduces genetic variability
* b. founder effect: when a few individuals
colonize a new area.
- evolution of flies on Hawaii. Species
on different islands have allele frequencies
that are different from original species on
mainland
17.2 Answers cont’d
15.
13. Genetic equilibrium = when allele
frequencies in a population remain the
same….no evolution is taking place
p = dominant allele frequency
14. HW Principle: allele frequencies in a
population remain constant UNLESS
one or more factors cause frequencies
to change.
p+q=1
5 conditions to maintain allele
frequencies:
p2 + 2pq + q2 = 1
q = recessive allele frequency
HW formula:
1. large population
p2 = % of population pure dominant
2. no mutations
2pq = % population hybrid dominant
3. random mating
q2 = pure recessive
4. no migration in or out
if p=.4 and q=.6, what % of the
population would be:
5. no natural selection
16- 17. when these happen: small
population, mutations, particular
mating, migration, and natural
selection happen,  evolution occurs
a) pure dom______
b) hybrid dom______
c) pure recessive______
17.3 Answers
18. Species: a population whose members
can interbreed and produce fertile
offspring
mixed species hybrids
Speciation: the formation of new species
19. Reproductive Isolation: allows for
members of one species to develop into
two different ones once reproduction is no
longer happening.
20. Can happen in these ways:
a) behavioral isolation: when courtship
rituals differ
b) geographical isolation: when
geographical barriers prevent
reproduction (river, mountain, ocean)
c) temporal isolation: when reproduction
occurs at different times of year or
day, etc.
17.3 Answers cont’d
1
4
21. Five steps to the 14 finch
species on the Galapagos
Islands:
1) founders arrive
2) geographic isolation
3) changes in gene pools
5
2
4) behavioral isolation
5) competition and continued
evolution
3
19.1 Answers
1. What do fossils reveal about ancient life?
Fossils tell us the structure of ancient organisms,
their environment and the ways in which they
lived.
2. What types of fossils exist?
Can be a whole organism, teeth, bones, leaf
pieces, droppings
3. What is relative dating? Describe how it works.
Relative dating: using the layers of sedimentary
rock, we can determine if a fossil is older or
younger than other fossils. Useful, but does not
give us an actual age in years.
19.1 Answers cont’d
4. What is radiometric dating? How is it done?
Radiometric dating: uses the proportion of
radioactive to stable isotopes to determine age of
fossil.
* use the known rate of decay of an isotope:
the “half life”
* half-life = the amount of time for 50% of the
radioactivity to decay
* half-life of 14C is 5730 years.
* in 5730 yrs, 50% remains (1/2)
* in ANOTHER 5730 yrs, 25% remains (1/4)
* in ANOTHER 5730 years, 12.5% remains (1/8)
•
What isotopes are used for recent
fossils and very old fossils? recent fossils:
14C older fossils: 40K or 238U
5. What time did humans appear? 11:58:56 pm
19.2 Answers
6.
What is a “clad”? What processes influence whether
species/clades will survive?
Clad = a group of species which includes a single
common ancestor and all descendants of that ancestor
* if rate of speciation is same as or greater than rate of
extinction, then clad will survive
* if extinction rate is greater than speciation rate, clad
will not survive.
7. What is the benefit of a mass extinction? Benefit was the
increase in diversity and speciation of those who
survived
19.2 Answers cont’d
8. Describe and explain the differences between punctuated
equilibrium and gradualism. Rate of evolution is thought to
be different for different species at different times in
history. Two methods:
1. gradualism: slow and steady change over time
2. punctuated equilibrium: long periods of little or no
change interrupted by periods of great change and rapid
evolution
9. Why does evolution happen faster in smaller populations?
Give an example.Smaller populations evolve faster
because genetic changes spread more quickly and are
seen more rapidly in a small group.
10. Describe the process that is adaptive radiation. Adaptive
radiation: process where a single species evolves in short
time into several different forms who live in different ways.
After dinos extinction, mammals showed a huge adaptive
radiation and diversification
*Galapagos finches show modern adaptive radiation
19.2 Answers cont’d
11. Look at (Fig. 19-11). Which mammal group is most closely
related to the elephants?The Sirenians (Manatee)
12. After the dinosaurs disappeared, what happened with the
evolution of mammals? Why was this? Mammals diversified
very quickly. Had more space, food, some predators were
extinct now.
13. Name 3 ways in which adaptive radiation may occur.
a) when species move to a new environment
b) when extinction clears an area of a number of
organisms
c) development of a new feature which makes a previously
unusable environment now accessible
14. What is convergent evolution? How does it happen? Explain
Fig. 19-12 with this concept. Convergent evolution: similar
environments select for similar features in organisms not
related through common descent.
• All anteaters have similar mouth structure due to
convergent evol.
• emus, ostrich, rheas all similar looking, but not related
19.2 Answers cont’d
15. What is “co-evolution” and how does it happen? Give
examples with flowers and plants. Co-evolution:the
relationship between 2 evolving organisms is so specific
that one can’t survive with out the other. A change in
one will bring about a change in the other
• Ex: flowers and pollinators. Some flower structures
require one or a select few types of insects to
access nectar.
• (ex: 40-cm long tongue of a moth to reach nectar
inside orchids on Galapagos)
• Ex: plants evolved bad tasting poisons so insects
won’t eat them
16. Once plants developed toxins to keep insects from
eating them, what happened? Natural selection
chose for those insects who could tolerate or use
the toxin.
**Monarch gets a free
defense weapon and no
Why will ONLY Monarch caterpillars feed on the
milkweed plant? Why does this exclusivity benefit competition from other
insects for the same food.
BOTH the milkweed and the Monarch? Monarch
caterpillars can tolerate toxin AND store it to use as Milkweed plant only eaten by
one type of insect
a defense from predators!
19.3 Answers
17. How did earth originate? Pieces of cosmic debris
crashing into each other
18. Describe the early atmosphere. Early atmosphere had
only CO2,H2O vapor, and N2. NO O2
Oceans contained high amount of iron.
19. Miller/Urey: Simulated the early atmospheric gases
energy sources. Amino acids were produced in the
“ocean” water flask.
and
20. First genetic material: RNA. Simpler as a single strand,
some RNA’s can help DNA replication, some can modify
mRNA pieces, some act as enzymes, some can replicate
on own.
21.Why were first life forms anaerobic? No O2 in early
atmosphere
22. Early photo bacteria released oxygen, made rusty
colored oceans. Great bands of iron are still mined on the
ocean floor today
19.3 Answers
23. What is the Endosymbiont theory? What evidence
supports this theory? The explanation of how
eukaryotic cells evolved from prokaryotic ones.
* infolding of cell membrane  nuclear envelope
and ER, golgi
* engulphment of smaller bacteria  mitochondria
and chloroplasts
* evidence: mitochondria and chloroplasts have
their own DNA and can replicate on their own
24. Why is sexual reproduction so vital to the
evolutionary process? Sexual reproduction
increases genetic variations that drives evolution