Darwin’s Voyage of Discovery
Evolution
The theory of evolution was created by an English scientist by the name of CHARLES
DARWIN.
Evolution: Change in species over time
Evolution
Biological Evolution theorizes how modern organisms evolved over a long period of time
through descent from common ancestors.
Darwin’s Voyage
1. 1831 Darwin began his journey traveling by a sail boat named the HMS Beagle
2. Voyage was taken along the coastline of South America.
3. Total voyage was five years.
4. Darwin collected specimens of different plants and animals and conducted
observations along the way.
Developments of distinctive patterns of biological diversity:
1.
2.
3.
Species vary globally
Species vary locally
Species vary over time
Evolution
Species vary globally
Flightless bird
1. Rheas lived only in the grasslands of South America (look and act like ostriches)
2. Ostriches live only in the grasslands of Arica
3. Emu lived only in the grasslands of Australia
Conclusion:
Different , yet ecologically similar animal species inhabited separately
SIMILAR species, SIMILAR environments, DIFFERENT locations
Indochinese tiger: only found in Asia, the slimmest body of all the tiger species
Sumatran Tiger: The darkest and most
striped of all the tiger species
South China Tiger: only found in South
China, the rarest, their fur is light
orange
Evolution
Species vary locally
Flightless bird
1. Darwin found two species of Rheas living in South America
Argentina’s grassland
Colder, harsher grass and scrubland to the south
Conclusion:
Different , yet related animal species occupied different habitats within a local area.
RELATED species, DIFFERENT environments, SAME area
Evolution
Mockingbird of South America
Wren bird of Argentina
Blackbird of South America
Warbler bird of Galapagos Island
Evolution
Species vary Over Time
Darwin also collected Fossils: Preserved remains or traces of ancient organisms
Marine Mollusks
Conclusion:
Some fossils of extinct animals were similar to living species.
EXTINCT species are similar to LIVING species
Evolution
Species vary Over Time
(A) Pan troglodytes, chimpanzee, modern
(B) Australopithecus africanus, STS 5, 2.6 My
(C) Australopithecus africanus, STS 71, 2.5 My
(D) Homo habilis, KNM-ER 1813, 1.9 My
(E) Homo habilis, OH24, 1.8 My
(F) Homo rudolfensis, KNM-ER 1470, 1.8 My
(G) Homo erectus, Dmanisi cranium D2700, 1.75 My
(H) Homo ergaster (early H. erectus), KNM-ER 3733, 1.75 My
(I) Homo heidelbergensis, “Rhodesia man,” 300,000 – 125,000 y
(J) Homo sapiens neanderthalensis, La Ferrassie 1, 70,000 y
(K) Homo sapiens neanderthalensis, La Chappelle-aux-Saints, 60,000 y
(L) Homo sapiens neanderthalensis, Le Moustier, 45,000 y
(M) Homo sapiens sapiens, Cro-Magnon I, 30,000 y
(N) Homo sapiens sapiens, modern
1.
2.
Charles Darwin conducted most of his experiments on an Island called Galapagos
He studied many animals and plants that were unique to the island, but similar to other
species elsewhere. Therefore he begin to question if different species evolved from South
American Ancestors
Darwin’s Theory of Evolution
Hutton and Geological Change
1.
Recognized the connection between
geological processes and features
(mountains, valleys, and layers of rock
develop from molt, rain, wind, heat
and cold over time).
Lyell’s Principle of Geology
1.
2.
1.
2.
Concluded – Earth must be older than
a few thousand years.
Introduced the concept of deep time
(Earth’s history is too long for man to
date back
Coined the term uniformationarianism,
which states that processes seen
today, must have been the same in
the past that shaped Earth millions of
years ago.
Ex: Volcanoes erupted back then and
released lava and gases, as they do
today
Lamarck’s Ideas
Jean Baptiste Lamarck
Organisms change and acquire
features that help them
survive in their environments.
(Ex. Water birds acquired long legs
because they began to wade in
deeper water looking for food.
Organisms could change their
individual structures by not
using them.
(Ex. Birds do not use their wings, so
the wings become smaller)
Traits altered by an individual
organism during its life are called
ACQUIRED CHARACTERISTICS
Inheritance of acquired
characteristics – Acquired traits
that are passed down to offspring
over generations
Lamarck’s Evolutionary Hypothesis
Organisms could change during their
lifetime by selectively using or not
using diverse parts of their body.
He proposed that these traits are passed
down to offspring, allowing change
over time.
His hypothesis was incorrect, as traits
acquired by individuals cannot be
passed to offspring
Jean Baptiste Lamarck
POPULATION GROWTH
English economist by the name of Thomas Malthus noted that humans were
being born faster than people were dying, causing overcrowding.
He reasoned that if the human population grew unchecked, there wouldn’t
be enough living space and food.
Forces that work against population growth:
a. War
b. Famine
c. Disease
From these findings Darwin questioned the mode of survival of the fittest.
There are two types of survival selection
 Artificial Selection
 Natural Selection
ARTIFICIAL SELECTION: Selective breeding of organisms to produce offspring with the certain
traits.
Darwin Presents His Case
Natural Selection: a process where organisms with strong traits survive and weak traits die
1. Occurs- in any situation where there are more individuals that are born than can survive
Classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Felidae
Genus/Species: Panthera tigris
The concept of EVOLUTION BY NATURAL SELECTION
1.
a.
b.
c.
Darwin concluded that members of a population must compete to get:
Food
Living space
Other life necessities that may be limited
2. Darwin hypothesized that some variation of traits are better suited for life and survival
Ex. Predators that are faster, stronger, and have longer claws can catch more prey.
3. An inherited characteristic that increases an organism’s ability to survive and reproduces in it’s
environment is called an ADAPTATION.
A.
Adaptations include:
- body parts (tiger’s claws)
- colors (camouflage, or mimicry). Ex. Camillion
- physiological function ( how a plant carries out photosynthesis)
- behaviors (how prey avoid predators, such as an armadillo curling up into a ball)
4. Darwin proposed that different adaptations affect an individuals fitness.
5. FITNESS – describes how well an organism can survive and reproduce in it’s environment.
6. Those organisms with a better chance of survival and reproduction due to their adaptations
are said to have high fitness.
7. Organisms that are not well suited for their environment and die off without reproduction or
leave few offspring are said to have low fitness.
8. The difference in rates of survival is called “Survival of the Fittest”
- note: survival means staying alive and reproduction and the passing of adaptations to the
next generation.
MODES OF NATURAL SELECTION
Struggle for Existence
Variation and Adaptation
Survival of the fittest
Natural Selection
Because the green color serves as a
camouflage from predators, the green
grasshoppers have a higher fitness than the
yellow ones.
Green grasshoppers become more common
than yellow grasshoppers in this population
over time.
Organisms produce more offspring than can
survive (Spider eggs)
There is a variation in nature called
adaptations that increase an individual’s
chance of survival and reproducing
COMMON DESCENT
1.
COMMON DESCENT- All species, living and extinct are descended from ancient common
ancestors “ Tree of life”
2.
Natural selection depends on the ability of organisms to reproduce, which means to leave
descendents.
COMMON DESCENT
3. Darwin proposed that
- over generations, adaptation could cause successful species to evolve into new species.
- living species are descended with modification from common ancestors – called descent
with modification
4. Hutton and Lyell contribution to Darwin’s theory :
- deep time gave enough time for natural selection to act.
- Darwin used the fossil record as evidence of descent with modification over long periods of
time
Evidence of Evolution
BIOGEOGRAPHY
How does the geographic distribution of species today relate to their evolutionary history?
1.
Key Concept 1 –Biogeography
a.
Biogeography = the study of where organisms live now and where they and their ancestors
lived in the pass.
b.
We are able to tell how modern organisms evolved from their ancestors by comparing living
and fossil species.
c.
Two biogeographical patterns are important to Darwin’s theory
1. closely related species differ in slightly different climates
EX. Over time, natural selection produced variations within populations that resulted in different,
but closely related species on the island of Galapogos.
2. distantly related species develop similarities in similar environments.
EX. Similar ground dwelling birds inhabit similar grasslands in Europe, Australia, and Africa.
( Differences in body structures among those animals provide evidence that they evolved from
different ancestors. However, similarities among the animals, provide evidence that distantly
related species to develop similar adaptations)
BIOGEOGRAPHY
How do fossils help to documents the descent of modern species from ancient ancestors?
2. Key Concept-2
a.
Many recently discovered fossils form series that trace the evolution of modern species from
extinct ancestors.
EX.
(A) Pan troglodytes, chimpanzee, modern
(B) Australopithecus africanus, STS 5, 2.6 My
(C) Australopithecus africanus, STS 71, 2.5 My
(D) Homo habilis, KNM-ER 1813, 1.9 My
(E) Homo habilis, OH24, 1.8 My
(F) Homo rudolfensis, KNM-ER 1470, 1.8 My
(G) Homo erectus, Dmanisi cranium D2700, 1.75 My
(H) Homo ergaster (early H. erectus), KNM-ER 3733, 1.75 My
(I) Homo heidelbergensis, “Rhodesia man,” 300,000 – 125,000 y
(J) Homo sapiens neanderthalensis, La Ferrassie 1, 70,000 y
(K) Homo sapiens neanderthalensis, La Chappelle-aux-Saints, 60,000 y
(L) Homo sapiens neanderthalensis, Le Moustier, 45,000 y
(M) Homo sapiens sapiens, Cro-Magnon I, 30,000 y
(N) Homo sapiens sapiens, modern
Anatomy
Scientist use structural similarities as evidence that organisms evolved from a common ancestor
HOMOLOGOUS STRUCTURE: body parts (structures) that HAVE a common evolutionary history
These structures are similar in arrangement, or in function or both
Anatomy
HOMOLOGOUS STRUCTURE: body parts (structures) that HAVE a common evolutionary history
These structures are similar in arrangement, in function or both
ANALAGOUS STRUCTURE: body parts (structures) that do NOT have a common evolutionary
history
These structures are similar in function, may be different in arrangement
ANALAGOUS STRUCTURE: body parts (structures) that do NOT have a common evolutionary
history
These structures are similar in function, may be different in arrangement
VESTIGIAL STRUCTURE: body structure in present-day organisms that no longer serves it
original purpose
This whale has a pelvic bone, but it is not used
In the function of the hips in humans
Penguins have wings, but they do not use them to fly
Mole rats have eyes, but they do
not use them to see
Structural Adaptations
Adaptations in species develop over (time) many generations .
Some structural adaptations are subtle like mimicry and camouflage
MIMICRY: adaptation that allows one species to resemble another
Moth caterpillar resembles a snake
hover flies resemble wasp and bees
CAMAFLAUGE: when an organism blends in with their environment
Cytochrome C
Cytochrome C – homologous protein
a. functions in cellular respiration
b. similar cytocrhome are found in all living cells
c. helped to determine evolutionary connections via chemical structures.
Hox Genes
Hox genes- determine the head-too-tail axis in embryonic development.
a. directs the growth of front and hind limbs.
b. minor changes in an organisms genome can have major effects on body structure
c. homologous hox genes are found in almost all multicellular organisms
d. This concept explains how living organisms evolved through descent with modification from a
common ancestor
Evolution of Populations
Evidence of Evolution
Populations, not individuals can change over time
How can a population’s genes change over time?
a. GENE POOL: all of a populations genes together
b. ALLELIC FREQUENCY: Percentage of a specific gene in a gene pool
Ex: looking only at blue eyes in a population
c. GENETIC EQUILIBRIUM: when genes remain the same over generations
Ex. Everyone in a population is 6 ft tall, with green hair and 7 fingers. These traits
remain the same for hundreds of years
d. GENETIC DRIFT: When genes change in a population, due to genes leaving or
entering a population
Populations, not individuals can change over time
How can a population’s genes change over time?
a.
SINGLE-GENE TRAIT: a trait controlled by only ONE gene
Ex. Gene for shell banding has two alleles.
The allele for bi bands is dominant over the allele for dark bands.
All genotypes for this trait have one of two phenotypes
- shells with bands and without bands
- single-gene traits may have two or three distinct phenotypes
b. POLYGENIC TRIATS: many traits are controlled by two or more genes.
Ex. Each gene for a polygenetic trait has two or more alleles.
Results in single polygenetic traits having many genotypes, causing difficulty in
distinguishing charactaristics.
Evidence of Evolution
Types of Natural Selection
There are 3 types of natural selection
Stabilizing selection
Directional selection
Disruptive selection
STABILIZING SELECTION: natural selection favors the average INDIVIDUAL in a
population
Ex. If you have a population of 20 people
16 people are red
4 people are blue
natural selection is going to look at 1 of the 16 red people
DIRECTIONAL SELECTION: Natural selection favors one of the two groups
Ex. There are 16 red people, 4 blue people
Natural selection will choose EITHER all the red people or blue people
DISRUPTIVE SELECTION: Natural selection will choose both groups
Ex. There are 16 red people , 4 blue people
Natural selection will choose BOTH red and blue
BOTTLENECK EFFECT: the change in allele frequency following a dramatic reduction
in the size of a population. Reducing genetic diversity
FOUNDER EFFECT: when allele frequencies change as a result of the migration of a
small subgroup of a population
Speciation: Creation of a new
species
Golden-mantled tree kangaroo
Evidence of Evolution
How can new species evolve or develop
GEOGRAPHICAL ISOLATION: occurs when a physical barrier divides a
population
Ex. Mountains, lakes, rivers, canyons, deserts, oceans
REPRODUCTIVE ISOLATION: occurs when formerly mating organisms, can
no longer mate and produce fertile offspring
Ex. A man and a Woman are able to mate, but something occurs and now they
can no longer mate and produce children
How fast can new species develop?
GRADUALISM: the idea that new species develop slow and gradual
PUNCTUATED EQUILIBRIUM: the idea that species develop rapidly , with
periods of no change (genetic equilibrium) in between
Patterns of Evolution
ADAPTIVE RADIATION: when
an ancestral species evolves
(develops) into a variety of
new species
( divergent evolution in which
ancestral species evolve into
an array of species to fit a
number of diverse habitats)
Divergent Evolution
New species are now distinct ( unique). You can tell them apart
(occurs when populations change as they adapt to different environmental conditions;
resulting in new species)
Ex. Bengal Tiger: has a pure white
Underbelly
Amur Tiger: Has the least stripes of all
tigers
Convergent Evolution
Distantly related organisms have the similar
characteristics because their environments are
the same
http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.
html
Hardy Weinberg Principle
Key Concept 1 – Hardy Weinberg Principle
a.
b.
States that allele frequencies in a population should remain constant unless
one or more factors cause those frequencies to change.
Makes predictions like punnet squares, but for populations, not individuals.
EX. Say there were two alleles for a gene:A (dominant) and gene a
(recessive).
A cross of these alleles can produce three possible genotypes: AA, Aa, and aa.
The frequencies of genotypes in a population can be predicted by these
equations, where p and q are the frequencies of the dominant and
recessive allele
Hardy Weinberg Principle
EX. In symbols
p2 + 2pq + q2 = 1 and p +q =1
In words
(frequency of AA) + (frequency of Aa) + (frequency of aa) = 100% and
(frequency of A) + (frequency of a) = 100%
EX:
In one generation , the frequency of A allele is 40 percent (p = 0.40),
Frequency of a allele is 60 percent (q=0.60)
If these genetic equilibrium, chances of an individual in the next generation
having genotype AA would be 16%
Hardy Weinberg Principle
genotype AA would be 16% (p2 = 0.402 = 0.16 or 16%)
The probability of genotype aa would be 36% (q2=0.602 =0.36 or 36%)
The probability of genotype Aa would be 48%
2pq = 2 (0.40)(0.60) = 0.48 or 48%
If a population does not show these predicted phenotype frequencies,
evolution is taking place
Hardy Weinberg Principle
b. Hardy- Weinberg principle predicts that five conditions can disturb
genetic equilibrium and cause evolution to occur