Download Genetic Engineering, Evolution, and Diversity

Genetic
Engineering,
Evolution, and
Diversity
Topic 23
I. Genetic Engineering
 A.
artificial selection - individuals with
desirable traits are mated to produce
offspring with those traits
 B. inbreeding - offspring with desirable
traits are mated with one another
 C. hybridization - two varieties of a
species are mated
 D.



Genetic research
1. Cloning - producing identical offspring
from a single cell of an organism
2. Genetic engineering - transfer of genes
from one organism to another producing
recombinant DNA – see example on board
3. Human Genome – mapped out human
DNA
II. Evidence of Evolution
 A.
evolution – idea that organisms have
changed over time – provides
understanding for the diversity of life on
earth
 B. fossil record

1. fossils – preserved impressions or remains of
organisms




a. hard bony parts
b. amber
c. tar
d. ice

2. dating of fossils
 a.
comparative dating – compare the fossils
with the layers that they are found in – does
not give an exact date
 b. radioactive dating to find the actual date
of the fossil – for example, use carbon 14

3. problems with fossils – although fossils
have revealed a great deal about how
organisms have changed, there are gaps in
history – these gaps are probably due to
the scarcity of fossils or a difficulty in finding
them – some people believe that the gaps
mean that evolution did not occur
 C.
Comparative Anatomy – examine
internal and external structures to find
similarities and differences

1. homologous structures – same
anatomical structures but perform different
functions – for example, the bones in the
wing of a bird and the bones in the flipper
of a whale are similar in structure but they
are used for different functions such as
flying and swimming

2. analogous structures – different structures
but similar functions – for example the
structure of the wing of a butterfly and the
wing of a bird are different in structure but
similar in function (flying)
 a.
convergent evolution – evolution of
structures that are the same for a common
function but not derived from a common
ancestor – analogous structures are not used
as a basis for classification

3. vestigial structures – structures that are no
longer used such as the appendix and the
tonsils – as things changed and evolved,
these structures were no longer needed –
the appendix for example is small and
useless in humans but assist digestion of
cellulose in herbivores indicating humanity’s
vegetarian ancestry
 D.
Comparative embryology –
comparison of embryos and embryonic
development
 E.
Molecular Evolution (part of
comparative biochemistry) – comparison
of genes and proteins to determine if
there is an evolutionary relationship – the
closer the genetic sequences, the more
closely related they are in evolution

1. molecular clock – the rate of change in a
gene over time
F. Comparative cytology – the study of similar
organelles found in a cell such as the
mitochondria or ribosomes
III. History of Evolutionary
Theories
 A.


Lamark
(1) use and disuse – organisms develop new
organs or change their existing ones in order to
meet their changing needs
(2) acquired characteristics – parents pass on
traits they acquire during their lifetime
 B.
Weismann - disproved Lamarck’s theory of
acquired characteristics by taking the tails off
of mice and allowing them to mate - none of the
offspring were missing tails
C. Darwin - theory of natural
selection - main theories:
a. overproduction - more offspring are produced in
each generation than can survive
 b. competition - individuals of each generation
compete for the available food and to reproduce
 c. variation - some organisms are better adapted to
survive
 d. survival of the fittest - individuals that are better
adapted will survive
 e. adaptations will be passed on to future generations


D. DeVries - discovered mutations which Darwin
failed to account for
IV. Rate of Evolution
 A.


rate of change
1. Gradualism - evolution occurs gradually,
slowly and continuously
2. Punctuated equilibrium - species tend to
stay the same for a long period of time and
then change quickly then stay the same for
a long period of time and then change
V. Heterotroph Hypothesis
A. heterotroph hypothesis - helps describe
how life may have begun on earth
B. primitive conditions - no free oxygen, had
hydrogen, ammonia, and methane - had
water, temp was very high - lots of energy
C. synthesis reactions - organic molecules
were made from inorganic molecules
D. aggregates of organic molecules organic molecules cluster together to
form aggregates
E. reproduction - aggregates got to be
large and started to split apart
(reproduce)
F. anaerobic respiration - released carbon
dioxide to the atmosphere
G. development of autotrophs - used
carbon dioxide to produce their own
food
H. aerobic respiration - autotrophic activity
releases oxygen which allows for aerobic
respiration
VI. Mechanisms of Evolution
 A.
Evolution does not occur in a single
individual but in a population of a species


1. population – group of individuals of the
same species that live in a certain area and
interbreed
2. species – group of individuals that are
able to breed with each other and
produce offspring that are able to have
more offspring



3. gene pool – all of the alleles in a
population
4. gene frequency – how often an allele is
found in the gene pool
5. sexual reproduction constantly mixes
alleles in a population which provides new
combinations – through meiosis and
random mating


6. mutations can create new alleles
7. evolution is caused by changes in the
gene pool of a population over time
 B.
Hardy-Weinberg principle and
population changes


1. allele frequencies in a gene pool of a
population determine how many individuals
in a population get each allele
2. in allele frequencies p (frequency of the
dominant allele) + q (frequency of the
recessive allele) = 1

3. Hardy-Weinberg principle
 Allele
frequencies in a population will remain
constant from generation to generation as
long as certain criteria are met:





(1) random mating must occur – no organisms
can be isolated
(2) no migration into (immigration) or out of
(emigration) can take place
(3) there must be no mutations
(4) large populations are required
(5) no natural selection

4. Mathematical formula for the HardyWeinberg equilibrium principle
example #1:
p stands for tallness and is .80
this means that q would have to be .20
because p+q=1 so 1-p=q so 1-.80=.20 so
q=.20
Example #2:
For a population, eggs x sperm = offspring
(p+q)(p+q) = p2 + 2pq + q2 = 1
p = frequency of dominant allele
q = frequency of recessive allele
p2 = frequency of homozygous dominant
individuals
2pq = frequency of heterozygous individuals
q2 = frequency of homozygous recessive
individuals
Example #3
In a certain population, the frequency of
homozygous curly hair (CC) is 64%. What
percentage of the population has curly
hair?
VII. Disruption of Hardy-Weinberg
Equilibrium in Evolution
mutation – provide a source of variation in a
population
 B. gene flow – if two populations are separated
from each other and do not interbreed, then the
allele frequencies in their gene pools may be
different from each other – if individuals move
between the populations, they create a gene
flow which alters the allele frequency
 A.
 C.




population size
(1) small population – random events can alter
the gene pool
(2) genetic drift – changes in the gene pool caused
by random events in a small population
(3) population bottleneck – if a flood suddenly
and dramatically reduces the size of a population,
the allele frequencies of the survivors are not
necessarily the same as the allele frequencies in
the original population
(4) founder effect – colonization of a new habitat
Nonrandom mating – Sexual selection –
mating must be random, however; individuals
are usually discerning in mate selection which
prevents the Hardy-Weinberg equilibrium
 D.
 E.



natural selection
(1) stabilizing selection - does not change the
average, but makes the curve around the average
sharper, so that values in the population lie closer
to the average
(2) disruptive selection – the peak value is
selected against – the two extremes are selected
for
(3) directional selection – alters the average value
for a trait
VIII. Speciation
speciation – creation of a new species –
occurs when the gene pool for a group of
organisms becomes reproductively isolated
 A.



(1) allopatric speciation – two populations of a species
are separated geographically or by a physical barrier
(2) adaptive radiation – production of a number of
different species from a singe ancestral species – called
divergent evolution – shown by Darwin’s finches
(3) sympatric speciation – speciation by populations
that occupy the same region – must be reproductively
isolated while still living in the same region – ex.
polyploidy