Transcript Chapter 22 ppt

1800
Darwin
Lamarck
1750
1900
Mendel
Linnaeus
Linnaeus (1707-1778)
- Classified and grouped organisms based on
their characteristics.
- Developed classification system (ex. humans)
- Kingdom (Animalia)
- Phylum (Chordata)
- Class (Mammalia)
- Order (Primates)
- Family (Hominidae)
- Genus (Homo)
-Species (sapien)
Back to Timeline
Lamarck (1744-1829)
Early evolutionist who believed in three principles
that drove evolution
1) Use and Disuse – Parts of the body that were
used developed, and other parts not in use did
not develop
2) Inheritance of acquired characteristics – traits
that an organism acquired during its lifetime can
be passed on
3) Species transformation – Acquired
characteristics is passed on to the subsequent
population
Back to Timeline
According to
Lamarck, the
giraffe’s neck grew
longer over time,
because of the
giraffe’s “desire” to
reach the higher
leaves. Since they
had to use their
neck muscles more
to stretch and
reach the upper
leaves, these
acquired traits
developed and
were passed on to
the subsequent
generations.
Gregor Mendel (1822-1884)
Augustinian monk, through his study of pea
plants helped father the study of modern
genetics
Back to Timeline
Charles Darwin (1809-1882)
- English naturalist who took a 5-year
voyage on the HMS Beagle and studied
the diverse species on the Galapagos
Islands
- Pubished his book The Origin of Species
in 1859, where he discusses his theory of
natural selection as the mechanism for
evolution
How do Darwin’s evolutionary
principles differ from Lamarck’s?
3. Differential Reproduction: You either have the genes
2.1)Genetic
Variation
- There
is diversity
in any
Heredity
Natural
selection
is
a
process
in do
which
to survive or you don’t. “Desire” has nothing to
with
population.
Genetic variation
in the population
canthat
some
individuals
have
genetically-based
traits
it. If you have genes that help your survival, you will
arise
due tosurvival
mutation
and
the shufflingGenes
of genes
inbe
improve
and
reproduction.
can
reproduce and leave behind more offspring with your
meiotic
processes.
passed
to the
next
generation.
genes thanon
those
who
don’t.
What is the general way we refer to
those who survive?
Fitness:
• An individual’s success at reproducing
– (the more offspring the individual leaves, the
higher its fitness).
• Fitness is dependent upon a particular
phenotype that individual has.
Evolution of Color in Beetle Populations
1. Genetic variation.
For example, some beetles are
green and some are brown.
2. Differential reproduction.
Since the environment can't support unlimited population
growth, not all individuals get to reproduce to their full
potential. In this example, green beetles tend to get eaten
by birds and survive to reproduce less often than brown
beetles do. The green beetles are less “fit”.
3. Heredity.
The surviving brown beetles have brown baby
beetles because this trait has a genetic basis.
How do we measure evolution?
Measure the allele frequency of genes for
both coloration before and after a certain
period of time
Overview of the Steps of Natural
Selection
1.
2.
3.
4.
Organisms have reproductive potential.
There is genetic variation in a population.
The genetic variation is heritable.
Environmental resources are limited and/or there
is a struggle for survival.
5. Individuals will compete to survive, so there is
differential reproduction.
6. The most fit will pass on its genes to the
subsequent generation, increasing its gene
frequency in the population.
7. Evolution is measured and is evident when allele
frequencies of genes change over time in a
population.
What are sources of genetic
variation?
1) Mutations - those created in gametes can be
passed on to the next generation (not those in
somatic cells)
2) Sexual Reproduction – creates individuals with
new, random allelic combinations
3) Diploidy – presence of two copies of each
chromosome in a cell
4) Polymorphism - (dominant/recessive interactions,
etc. in diploid organisms)
5) Quantitative characters – added effect of 2 or
more genes on phenotype (ex. height)
6) Neutral Variation – natural variations that do not
offer any selective advantage (ex. Fingerprints)
Misconceptions about Natural
Selection
• It is not “Survival of the Fittest;” really it is
“Survival of the ‘fit enough’”
If A = normal
blood and a =
sickle cell
blood, then . . .
AA = normal
Aa = normal
aa = sickle cell
Recessive alleles for
disease can stay
unnoticed in a population
Misconceptions about Natural
Selection
• Sometimes heterozygotes are more “fit”
than homozygotes…
• For ex. sickle cell carriers (Aa) are also
resistant to malaria
• This is called heterozygote advantage
Misconceptions about Natural
Selection
• Sometimes fitness is dependent upon
population frequency
• Ex. Minority advantage
– when rare phenotypes have an advantage
over the more common phenotypes
– As rare phenotypes increase in population,
they lose their advantage
– Often seen in predator-prey situations
What evidence do we have of
evolution?
1. Homologous Structures – Similarities in physiology
due to common ancestry in differing species
What evidence do we have of
evolution?
2. Vestigial Structures – Structure of marginal
importance to an organism that may have served a
more important function in its ancestors… ex. leg bones
of a snake
What evidence do we have of
evolution?
3. Embryological Homologies – similarities found in the
embryonic development of related species
What evidence do we have of
evolution?
4. Molecular Homologies – similarities found at the
molecular level of related species…ex. DNA, RNA, AA
What evidence do we have of
evolution?
5. Fossil Record – reveal pre-historic existence of past
species as well as those related species still in
existence
What evidence do we have of
evolution?
Blue-footed boobie from
Galapagos Islands
6. Biogeography – the geographic distribution of
species
ex. evolution of “endemic” species on islands that are
found nowhere else in the world
What current examples do we have
of evolution?
1. Insecticide
Resistance
- Application of
insecticides kill
insects w/o
resistance, but
promotes the
reproduction of
those with
resistance
What current examples do we have
of evolution?
2. Drug resistant HIV
- 3TC HIV drug
works by mimicking
the nitrogenous
base Cytosine
- within 4 weeks,
HIV resistant strains
appeared, with the
ability to distinguish
between 3TC and
Cytosine