Title: Evolution
1Evolution
- Chapter 15
- Darwins Theory of Evolution
215-1 The Puzzle of Lifes Diversity
- Biological Diversity- variety of living things.
- Evolutionary Theory- a collection of scientific
facts, observations hypotheses it can explain
the diversity of life on Earth. - Evolution- change over time the process by which
modern organisms have descended from ancient
organisms. - Scientific Theory- a well supported testable
explanation of natural events supported by
evidence can be tested with new evidence.
3Charles Darwin
- Contributed more than any other scientist to our
understanding of evolution. - Voyage of the Beagle- sailed around the world
stopping at the Galapagos Islands. - He made observations collected evidence.
- He noticed many plants animals were well suited
to their environment. - He collected fossils- preserved remains of
ancient organisms. - He collected many different species he had never
seen before.
4Evolution- Contributing Scientist Timeline
5Galapagos Islands
- Islands west of South America that are close
together but have very different climates. - Darwin studied shell shape of the many different
tortoises. - He discovered many similar but different birds
that turned out to be finches. - Each species of finch had a different shaped beak
which was a structural adaptation. - Darwin felt the animals on all the different
islands once came from the same species or common
ancestry.
6Voyage of the USS Beagle
715-2 Ideas that shaped Darwins Thinking
- He felt that many would find his ideas too
shocking to accept. - He began to put all of his work on paper.
- Several scientists influenced Darwin
- Hutton
- Lyell
- Lamarck
- Malthus
815-3 Darwins Case
- He was reluctant to publish his ideas because
they were so radical. - He was disturbed by his own findings which
challenged fundamental scientific beliefs. - When he heard a scientist name Wallace had the
same idea as his, Darwin published his work.
9Darwin Published his Book
- On the Origin of Species 1859.
- The book provided evidence that evolution has
occurred. - His theory on how evolution comes about was based
on artificial selection. - He believed that natural selection occurs in
nature.
10Artificial Natural Selection
- Artificial Selection
- Animal breeders select for breeding only animals
with the desired traits. - Ex. Crops, livestock horses.
- Natural Selection
- Individuals differ some of the differences can
be passed on to their offspring. - More offspring are produced than can survive or
reproduce. - Individuals best suited to their environment
survive reproduce most successfully. - Ex. run fast, outsmart with behavioral
tactics.
11Artificial Selection Man Made
12Survival of the Fittest
- Animals prey on other animals. Some die and some
survive. - Fitness- the ability to survive reproduce in a
specific environment. - Only the fittest organisms pass on their traits,
thus the species change over time. - Adaptation- an inherited characteristic that can
be physical or behavioral.
13Pesticide-Resistant Insects Modeling Adaptations
14Principle of Common Descent
- All species come from common ancestors.
- It links all organisms on Earth into a single
tree of life. - Ex. Tigers-panthers-cheetahs,
felines-horses-dogs-bats, mammals-birds-alligators
-fish.
15Genetic Evidence of Commn Decent
164 Types of Evidence to Support Evolution
- 1. Fossil record- comparing fossils from older
younger rock layers documents the fact that
evolution has occurred it is a detailed record
of evolution. Pg. 382,15-13 - 2. Geographical distribution of living species-
the presence of similar environments suggests
natural selection. Ex.-the finches could have
descended from common ancestors on the mainland.
Pg. 383, 15-14
174 Types of Evidence to Support Evolution
- 3. Homologous structures of living organisms-
they have different mature forms but develop from
the same embryonic tissues. Bone structure is the
same but they look different. All are adapted to
survive in different environments. Ex. Legs,
wings, fins. Pg 384, 15-15 - Vestigial organs- some homologous structures no
longer serve important functions in descendants.
Their size is reduces.
18Homologous Structures
194 Types of Evidence to Support Evolution
- 4. Similarities in early development, or
embryology- early stages, or embryos, of many
animals are very similar. Pg. 385, 15-17
20Evolution
- Chapter 16
- Evolution of Populations
21Definitions You need to know
- Genotype The genetic makeup of an organism EX
genes coding for blue eyes of genes coding for
brown eyes - Phenotype The physical appearance coded for by
the genotype- EX Do you have blue eyes or brown
eyes? - Allele The different forms of genes that code
for different traits
2216-1 Genes Variations
- What we already know
- Traits are controlled by genes.
- Many genes have at least 2 forms (or alleles).
- Individuals of all species are heterozygous
(meaning they carry genes for trait they dont
show) for many genes.
23Living Things have 2 copies of every chromosome-
One from the female parent and one from the male
parent
24Figure 14.3 Alleles, alternative versions of a
gene
25Different Alleles code for Different Phenotypes
(physical appearances)
26Genetic Variation
- Studied in populations
- Population- a group of individuals of the same
species that interbreed share a common group of
genes. - Gene Pool- results from interbreeding in
populations its all the genes that are present
in a population contains 2 or more alleles
(forms) for each inheritable trait. - Relative Frequency- the of times the allele
(trait) occurs in a gene pool, compared with the
of times other alleles (traits) for the same
gene occur its often a . Pg. 394, 16-2 - Ex. An allele makes up ¼ of populations allele
for a given trait. The relative frequency is
25. - In genetic terms, evolution is any change in the
relative frequency of alleles (or traits) in a
population.
272 Main Sources of Genetic Variation
- Mutations
- Gene Shuffling
- Occurs during gamete (egg sperm) production
results in many different combinations. - Compare populations gene pool to a deck of cards.
Shuffle you get a different hand each time but
it never changes the of kings, aces, etc. The
traits are still there, the of times they
appear just changes.
28Polygenic Trait
- Can have many possible genotypes (gene
combinations), producing many possible phenotypes
(physical appearances). - Controlled by 2 or more genes, each may have more
than one allele (or form). Ex. Height. - Bell Shaped Curve Pg. 396, 16-4
- How phenotypes are expressed.
- Most people are in the middle of the curve
29Polygenic Traits result in many different
phenotypes (appearances)
30Polygenic Trait Bell Shaped Curve
3116-2 Evolution as Genetic Change
- Natural Selection acts directly on phenotype
(physical appearance). Ex. Lizard color. Pg.
397, 16-5 - Natural selection on Polygenic Traits is more
complicated because more than one gene works on
the physical appearance.. - Directional
- Stabilizing
- Disruptive
32Directions, Disruptive Stabalizing Selection
33Directional Selection
- When individuals at one end of the bell-shaped
curve have higher fitness than individuals near
the middle or the other end of the curve. - The curve shifts toward the higher fitness end.
- Ex.- birds with larger beaks will have higher
fitness if a small-medium seed shortage occurs.
Pg. 398, 16-6
34Stabilizing Selection
- When individuals near the middle of the curve
have higher fitness than those on either end of
the curve. - This is where the average form of trait is.
- The curve narrows around the middle
- Ex.- a babies birth weight. Less wt., lower
survival rate. Higher wt., difficult birth.
Pg. 399, 16-7
35Disruptive Selection
- When individuals at the upper and lower ends of
the curve have higher fitness than the
individuals near the middle. - The curve develops a peak at each end and a low
point in the middle. - Ex.- Medium bird seed has a shortage. Small
large bird seed are abundant. Birds with small
large beaks will have greater fitness. Pg. 399,
16-8
36Genetic Drift- Contributes to Natural Selection
- Trait frequencies change.
- Occurs in small populations.
- Individuals with a particular trait leave more
descendants than other individuals. - Traits become more or less common by chance.
- The only similarity to natural selection is that
they involve a change in a populations trait
(allele) frequencies.
37Genetic Equilibrium
- A situation in which allele (or trait)
frequencies of a population remain constant. - 5 conditions required to maintain genetic
equilibrium - Random mating.
- Population must be very large.
- There can be no movement into or out of the
population (migration). - No mutations.
- No natural selection
- When all 5 are met, evolution will not occur.
3816-3 Process of Speciation
- Speciation- formation of new species
- For 1 species to evolve into 2 new species
- Gene pools of 2 populations must become
separated. - They must be reproductively isolated.
- Ex. finches on the Galapagos islands.
39Two forms of Speciation Gradualism Vs.
Punctuated Equilibrium
40Reproductive Isolation
- When members of 2 populations cannot interbreed
produce fertile offspring. - Behavioral- different courtship rituals.
- Ex. Songs.
- Geographical- populations are separated by
geographic barriers. Ex. Mountains, rivers. - Temporal- populations reproduce at different
times. Ex. Pollination.
41Geographic Reproductive Isolation
42Speciation of Darwins Finches
- The species evolved on the Islands from a single
species of founding birds. - They traveled from mainland South America to one
island to found a new population. - They survived reproduced then crossed to a 2nd
island. - The became geographically isolated gene pool
was no longer shared. - Seed size on the island favored large beak birds.
- Large beak birds reproductively isolated
evolved into a new species.
43Analogous Vs. Homologus Structues
- Analogous Sturctures Structures of different
organisms that have similar functions. DO NOT
RESULT from a shared common ancestor, but from
similar environmental demands EVIDENCE OF
NATURAL SELECTION EX bird wings insect wings. - Homologous Structures anatomical structures or
behavioral traits within different organisms
which evolved from a structure or trait of their
common ancestral organism. EVIDENCE OF COMMON
ANCESTRY EX Bat Wing, Whale fin human arm
44Analogous Vs. Homologous