2. Charles Darwin
• developed a scientific
theory of biological
evolution that explains
how modern organisms
evolved over long
periods of time through
descent from common
ancestors.
– The process of
change over time is
called evolution.
3. Species Vary Globally
• different, yet ecologically similar, animal
species inhabited separated, but
ecologically similar, habitats around the
globe.
• Rabbits that live in the grasslands in
England don’t live in the grasslands in
Africa!
• Do we have Kangaroo’s living in the wild
in the US?
4. • flightless, ground-
dwelling birds called • Ostriches
rheas living in the only live in
grasslands of South Africa
America
• look and act a lot like
ostriches.
• Only live in South
Africa
• Emu’s only
live in
Australia
5. Species vary Locally
– different, yet related, animal species often
occupied different habitats within a local area.
6. Turtles in Galapagos
• All the Islands have different climates
– Isabel Island has high peaks, is rainy, and has
abundant vegetation that is close to the ground.
– A tortoise from Isabela Island has a dome-shaped
shell and short neck.
– Hood Island, in contrast, is flat, dry, and has sparse
vegetation.
– A long neck and a shell that is curved and open
around the neck and legs allow the Hood Island
tortoise to reach sparse, high vegetation.
8. Species Vary over Time
– Darwin also collected fossils, which are the
preserved remains or traces of ancient
organisms.
– Darwin noticed that some fossils of extinct
animals were similar to living species.
10. Charles Lyell
-uniformitarianism- the
idea that the geological
processes we see in
action today must be
the same ones that
shaped Earth millions of
years ago.
-Volcanoes
-rivers dig canyons and
channels
11. Niagra Falls
• The force of the water wore away the rock layers and
Niagara Falls moved upstream, eventually reaching its
present location.
• Gradual erosion and periodic rockfalls steadily move
Niagara Falls farther upstream
12. Jean Baptiste Lamark
• organisms could
change during their
lifetimes by
selectively using or
not using various
parts of their bodies
• individuals could pass
these acquired traits
on to their offspring,
enabling species to
change over time.
13. Lamarck
• All animals strive to become perfect?
– NOT TRUE!!!!!
• inheritance of acquired characteristics-
traits acquired during a lifetime can be
passed on to offspring
– NOT TRUE!!!!!!
14. Thomas Malthus
• If the human
population grew
unchecked, there
wouldn’t be enough
living space and food
for everyone
15. Darwin Thinks about Malthus
– reasoning applied even more to other
organisms than it did to humans.
– most offspring die before reaching maturity,
and only a few of those that survive manage
to reproduce.
16. Neo-Darwinism
• Natural selection chooses the most
advantageous traits for an organism so that
those traits are passed on to future generations
– DOES NOT CREATE NEW GENES
• Mutations cause the changes in genes and
account for the variety of life today
• Darwins theory of evolution was revised to
include our knowledge of geneticts. The revised
theory is Neo-Darwinism.
18. The First Cells
• Autotrophs were the first cells
– Photosynthetic- convert CO2 & water to
glucose
– Chemosynthetic-live in extreme environments
• Scientists believe that the presence of
photosynthetic bacteria helped to form the
atmosphere as we know it today
19. • Oxygen would hurt Anaerobic cells
• Anaerobes must have evolved into
Aerobic cells to use the excess oxygen to
produce energy
• This leads us to the…..
20. Endosymbiotic Theory
• A large anaerobic primitive cell engulfed
an aerobic prokaryote to form a symbiotic
relationship with it.
• This bacterium may have become a
mitochondrion over time (have their own
DNA, divide by binary fission)
• This symbiotic relationship resulted in the
first aerobic eukaryote.
• All other eukaryotic cells evolved from this
cell.
23. Elements of Natural Selection
1. All species have genetic variation
2. Individuals within a species frequently
compete with each other for survival
3. The environment presents challenges to
an organisms survival
4. “survival of the fittest”
5. The traits of an organism best suited to a
habitat tend to become more frequent in
a population over time
25. Population
• Made of organisms of the same species
that live in the same place at the same
time
26. Think About it!
• Let’s suppose that a wild rabbit population
that lives in a densely wooded area has
genes that can produce white offspring,
brown offspring or black offspring. How
could environmental factors and natural
selection affect which trait for fur color
occurs most often?
27. Stabilizing Selection
• When natural selection favors average
individuals
• Insects want to be average size
– BIG insects are more likely to be consumed
–
Tiny insects can’t capture their food
28. Directional selection
• Favors an organism with an extreme trait
• Galapagos Finches
– During a drought food became scarce the
finches with larger beaks were better suited
for survival
29. Disruptive Selection
• Favors organisms with extremes in both
directions and eliminates the traits in the
middle
• If there was only really small bird seed and
really big bird seed, then only birds with
really tiny beaks and really big beaks
would thrive!
30. Hmmm…..
• In humans, infants with a low birth weight
or with a high birth weight are less likely to
survive. Which type of natural selection is
seen in the birth weight of humans?
• Lets suppose that the wild rabbits living in
a heavily wooded area have genes for
various shades of brown fun color. If a
mutation occurs to produce offspring that
are albino, would the mutation be harmful
or beneficial?
31. Adaptations
• Specific characteristics that help animals
survive in their environment
• Can be physical or behavioral
• Cats have claws to catch prey, pointed
teeth to tear apart food.
32. Critical Thinking
• A mutation occurs in a plant that causes
its leaves to taste bitter. In what kind of
environment would this mutation be
beneficial and more likely passed on to
future generations?
34. Importance of Diversity
• Diversity- a variety of traits that might be
passed on from generation to generation
• Gene pool- the total number of genes that
account for different traits in a species
• Species with a large gene pool have more
diversity and a greater ability to adapt
• A small gene pool limits diversity and can
traits can be lost for a number of reasons
35. Reason #1- Natural Selection
• Environmental factors often favor some
genetic characteristics over others
• Specific traits may be favored over others
to the point that undesirable traits can no
longer be found
36. Reason #2- Genetic Drift
• Change in a gene pool generated by
chance
• Instead of the environment selecting a trait
mere chance causes one trait to occur
more often than others
• Occurs more often in small populations
37. Reason #3- Founder effect
• The threat of extinction causes very few
organisms to be available to mate
• If the species recovers only the genes in
the limited gene pool get passed on
• The new gene pool may favor a different
trait than the original population
38. Reason #4- Selective Breeding
• Humans can use artificial selection
through selective breeding
• Wheat used to grow wild and had large
diversity
• Farmers chose the wheat plants that grew
the best and the “undesireable” traits
decreased
• Wheat is now uniform but subject to
diseases and pests
39. Reason #5- Mutations
• Add genetic variation
• In a stable environment they may be
harmful or have no benefit
• In a changing environment they may allow
an organism to adapt
40. Antibiotic and Pesticide
Resistance
• Bacteria mutate easily and as a result
bacteria acquire antibiotic resistance in
only a few generations.
• Mosquitoes are resistant to DDT
43. Geographic Isolation
• When an event creates a physical barrier
that divides a population into 2 or more
separate groups.
• Volcanic Eruptions or separation of a land
mass
44. Temporal Isolation
– When a species develops different
reproductive cycles ( ex. A spring and fall
cycle)
• Spring breeders will not breed with fall
breeders and the 2 groups slowly drift
apart
45. Behavioral Isolation
• Occurs when 2 populations do not
interbreed because of differences in
courtship behaviors.
• 2 similar species of birds may be capable
of producing fertile offspring but because
of different mating songs they will not
interbreed
47. Relative Dating
• Dating of fossils tells which fossils are
older than other fossils based on where
they are found in sedimentary rock layers
• The farther down the older
Radiometric Dating
• Tells the approximate age of a fossil by
measuring the amount of radioactive
isotopes found in the fossil.
48. Punctuated Equilibrium
• Suggests that long intervals in which little
or no change occurs are suddenly
interrupted by short bursts of quick, radical
transitions.
• Scienctists now believe in a combination
of gradual and punctuated
49. Comparative Anatomy
• Homologous-develop from the same
tissues as embryos and have similar
internal structures
– Common structures
• Analogous- have similar functions but
have not evolved from the sam ancestor
50.
51. Comparative Anatomy
• Vestigal Structures- structures that seem
to have no useful purpose now but
resemble useful structures in other
animals
– Ostrich wings, cave salamander eyes
• Embryology-embryos of many vertebrates
look similar
– If the embryos look alike they might have the
same ancestors
52. Biogeography
• How plants and animals are distributed
around the world
• Depends on migration patterns
• The distribution is used to figure out how
and when species may have evolved
54. Divergent Evolution
• New species “diverge” or split from a
common ancestor
– Homologous structures are evidence
– Adaptive radiation- one ancestorial species
splits into many related species
• Darwin’s Finches
55. Convergent Evolution
• Organisms that have similar
characteristics but are not considered
closely related
– Sharks and porpoises
– Analogous structures are evident
56. Coevolution
• When 2 organisms are dependent on one
another for survival
– Flowering plants and the specific insects that
pollinate them
