Transcript Unit 3- Evolution of Animals

Mrs. Stahl

Has a pink snout that is especially good at finding food. The snout’s
22 fingerlike projections can touch up to 12 objects in just one
second. The mole uses it’s paddle shaped feet for burrowing, and
its large ear openings give it excellent hearing. Has very poor
vision. How could evolution lead to this?


It forages at a rate so fast that the human eye
can barely register them. They have been
recorded at eating prey at 1/4th of a second.
Hypothesis- the reason they eat so fast is the
fact that its prey is so tiny, the mole must eat
twice as fast as animals that eat larger prey.

How do these traits arise in the
first place?
 Mutations
that have been passed
down from generation to
generation

What other factors could have
contributed to the star nosed moles
distinctive features over
generations?
Changes to their environment
 Prey
 Competing organisms





In front of you there are a series of pictures.
Look for pictures of animals that share physical
features (examples wings, horns, claws) but are
not necessarily closely related.
You decide the type of group!!!! Look at the
physical characteristics.
You have 5-10 minutes to complete this.
Present to class and give reasons for the choices
you made.


1. What is the source of the shared
characteristics in closely related species?
2. Why do distantly related species share
similar traits?


1. Shared genes
2. They occupy similar environments and
therefore may need similar features to move,
feed, find shelter, and survive


1. Shared genes
2. They occupy similar environments and
therefore may need similar features to move,
feed, find shelter, and survive.

Process of biological change by
which descendants come to differ
from their ancestors.

A group of organisms so similar that they can
reproduce and have fertile offspring.

Group of the same species that live in the same
area at the same time. They share unique set of
genes.




Started with the Greeks
Empedocles (495-435 BC) and Aristotle (384 322 BC)-> described concepts of change in
living organisms over time.
Carolus Linnaeus (1700’s)-> developed a
classification system for all organisms at that
time based on similarities.
George Lewis Buffon (1707-1788)-> studied
comparative anatomy relationships among
organisms and biological variation.

Erasmus Darwin (1794-1796)- Darwin's grandfather.
He said that all living things were descended from a
common ancestor.


Jean Baptiste Lamarck (1809)- zoologist who
studied animal classification, theory of inheritance> organisms develop new organs or modify
existing organs, as the need arises. If they do not
use them then the organs degenerate and are
changed based on environmental conditions. Also
believed that animals did not become extinct but
evolved into new animals.
Ex- giraffe= ancestral giraffes had short necks (like
other mammals) but they strained to reach higher
branches during feeding which resulted in
acquiring higher shoulders and necks.



Criticized heavily for this idea
We now know that it is not correct because there is
no evidence that changes in the environment can
initiate changes in organisms that can be passed on
to future generations. Change originates in the
process of gamete formation.
Random changes in DNA such as mutations, and
chance processes involved in the assortment of
genes into gametes (sex cells) result in a variation
of offspring. The environment plays a role in
determining the survival of these variations.

Darwin believed that giraffes evolved by which
the gene for long necks became dominant over
the gene for short necks. Giraffes with short
necks died out and giraffe with long necks
survived.
 Fossils-
traces of organisms
that existed in the past. The
deeper they are found in the
rock layers, the older they are.



1. Catastrophism- natural disasters such
as floods and volcanic eruptions have
happened often during history shaped
landforms -> caused species to become
extinct. These are sudden disasters.
2. Gradualism- slow changes over a
period of time. Ex- Pangaea
3. Uniformitarianism- geologic process
that shaped Earth are uniform through
time. Uniform= staying the same.

Volcanoes,
earthquakes, and
floods = Mass
Extinctions.

Canyons
carved by
rivers show
gradual
change.
Changes occur
in small steps
over time.

Rock strata demonstrates the geological
processes, which over time shows great change.
http://www.youtube.com/watch?v=CCIa
cOeB9cs




Named for the Galapagos tortoises
Tortoise shells were different in different
parts of the Albemarle Island.
Drier regions= the tortoises had longer
necks. There was high growing
vegetation in those regions.
Wetter regions= the tortoises had shorter
necks. There was low growing
vegetation.




The tortoises on the islands derived from a few
ancestral animals that traveled from the mainland.
There is no connection to the mainland (900 km away
= 559 miles).
The Galapagos are volcanic and arose from the
seabed. They have never touched the mainland.
Hypothesis- tortoises floated on mats of vegetation
that regularly break free from the coastline during
storms. The tortoises didn’t have any predators =
high population.
Also found on the Galapagos
Islands.
 1 species turned into 14 different
species
 Originals probably fed on seeds
and now some feed on plants,
insects, seeds, and cactus.





Open habitats and few predators allowed the
radiation of finches into 14 different species.
Adaptive radiation= formation of new forms
from an ancestral species usually in response
to the opening of new habitats.
Each species is adapted to a specific habitat on
the islands.
Biggest difference = diet, which was reflected
in the size and shape of their bills.


http://www.youtube.com/watch?v=03YKT7y
tJdE
http://www.youtube.com/watch?v=FT3FU2XOgo&feature=bf_prev&list=PL8D27E
2A18D8C3A7F
 Finches
and tortoises
convinced Darwin that
animals change over time.

The world’s oldest living animal- Harriet, a
Galapagos Island tortoise- was once Charles
Darwin’s shipmate. She was one of three Galapagos
tortoises captured by Darwin during his expedition.
Darwin took the animal back to England, and
thinking all three were males, named them Tom,
Dick, and Harry. The animals were poorly adapted
to the cool English climate, the animals were moved
to Australia around 1840. In the 1960’s scientists
realized that Harry, the last remaining member of
the trio, was actually a female. In 1992, DNA testing
suggested that Harriet was born around 1830.
Harriet lived at the Australian Zoo until her death
in 2006. She was around 176 years old.




Sea lions in the Galapagos suddenly lose
their main food source when changes in sea
temperatures and currents keep anchovies
away from the islands. The only food
available is small species of crab that lives
on the sea floor, 100 feet below the surface.
1. What traits in the sea lion population might
be adaptive?
2. How would the population change?
3. Write a description of the possible outcome.


1. They could travel for days to find sardines.
2. El Nino is the result of changes in wind patterns
and ocean currents that occur occasionally in the
winter. The warm tropical water moves eastward
across the Pacific and accumulates along the North
and South American coasts. Hard on places like
Ecuador and the Galapagos because they are highly
productive areas with nearly constant upwelling of
deep, nutrient-rich water.
 Outcome- warm water kills cold water organisms that are
the basis of the food chains for many marine birds,
mammals, and fishes. The loss of food causes the death of
these animals or the animals relocate.
http://video.nationalgeographic.com/video/environment/environment-naturaldisasters/landslides-and-more/el-nino/

3. Streamlined body
allows them to swim
fast and efficiently.



Survival of the fittest. They either adapt to
survive or die.
Pups may have the hardest time because they
are just learning to swim and hunt. They may
die off faster than the adults.
Adults may leave the area and travel to where
there is food.

Write a brief description
summarizing the scenario on a
separate sheet of paper.


Defined as-> individuals that have inherited
beneficial adaptations produce more offspring on
average than do other individuals.
Darwin came up with this after reading Thomas
Malthus’ essay entitled “Essay on Principles of
Population.”

He stated that the human population has the potential to
increase by doubling or by some other multiple rather than
by adding a fixed # of individuals.


Resources can’t keep up, therefore
things / factors such as poverty,
wars, plagues, and famines begin to
influence populations.
Darwin put it together that a similar
struggle occurs in nature -> Natural
Selection

1. All organisms have a greater reproductive
potential.




Example- Oysters release 100,000 eggs
Example- Female sea star releases about 1 million eggs.
Example- Robin lays four fertile eggs each season.
What would happen if all of these eggs
were fertilized and developed to
reproductive adults? What would happen
to the resources?
Overpopulation
 No room in the habitats
 Competition for resources such
as food, mates, habitats, etc.



Arises from a variety of
sources such as mutations,
genetic recombination
(crossing over), and
random fertilization.
Some genetic variations
may confer an advantage
to the individual that has
them. Some may be
harmful like severe
mutations.




Existence is a constant struggle
Many individuals die because there are too
many and not enough resources.
Individuals that die are those with traits that
make successful reproduction less likely.
Traits that promote successful reproduction are
adaptive.


Become more common from generation to
generation.
Example- Hummingbirds long bill.

1. Thorn Bug

Thorn Bug- makes predators less likely
to eat them.

Adapts to different habitats and feeding
strategies.



Large teeth and jaws -> eat shelled reptiles.
They will have more offspring and survive
than the ones that can eat only mammals.
Over generations these heritable traits became
more common.

Inflates when threatened by a predator.
https://www.youtube.com/watch?v=OkX
hC7yzISI

Learn to wash their potatoes before
eating them by imitating the
behavior of others.
https://www.youtube.com/watch?v=euMlL9O1Kc

Broad wings are adapted for silent flight > nocturnal bird that’s quiet and a deadly
predator.





Wings that produce flight
Strong flight muscles that move wings
Active metabolism-> energy for muscles
Hollow bone structure (less weight)
Reproductive adaptations
https://www.youtube.com/watch?v=ynlL8L3Ui8

Live in dry grasslands / desert Australia
(1 rainy season). Dry periods last for
about 10 months where the frog burrows
underground. They form a cocoon with
their shedded skin to keep moisture in
when it rains-> they crawl out to mate->
females lay eggs in puddles-> after two
weeks eggs hatch into tadpoles. If they
don’t adapt, they die.
https://www.youtube.com/watch?v=tuW https://www.youtube.com/watch?v=vtw
o_kWMihs
uL-znElQ


Some structures take new functions- adaptive
compromise.
Have a structure in their wrist that acts like a thumb. It
looks like they have six digits (five look like fingers),
but one is thumb-like and is actually an enlarged wrist
bone.

The bone is
actually called
a sesamoid
bone and is
small and
round. Your
kneecap or
patella is also a
sesamoid bone
that functions
as a pulley
systemincreasing
leverage of the
tendon as it
moves across
the joint.
five digits
wrist bone


https://www.youtube.com/watch?v=006ip4n
dThE
https://www.youtube.com/watch?v=aKh3kzx
U06Q
Artificial Selection
 Heritability
 Natural Selection



Humans change a species by breeding it for
certain traits.
Humans decide which traits are favorable and
then breed those individuals that show those
traits.
neck feathers
crop
tail feathers




Ability of a trait to be passed down from one
generation to the next.
Key factor in making artificial selection
possible.
Humans must breed the desirable traits such as
neck feathers, large crops, or extra tail feathers
in pigeons.
Humans don’t let it “just happen” they are the
selective agent not the environment.


Individuals that have inherited beneficial
adaptations produce more offspring on
average than do other individuals.
Environment is the selective agent- only the
strong / advantageous characteristics are
passed on to future generations.
 1.
Variation
 2. Overproduction
 3. Adaptation
 4. Decent with Modification


Individuals differ because the genetic material
is different, whether inherited from the parents
or resulting from a genetic mutation.
Ex- Jaguar. See attached example sheet in
notes.

Producing too many offspring at one
time. They won’t all survive because they
will die off while competing for
resources.

Certain variations or
characteristics allow an animal to
survive better than other
individuals.

Over time, species with adaptations that are
well suited for the environment in which they
live in, will survive and reproduce more than
others.



11,000 years ago many jaguars faced extinction
due to lack of food because the climate was
changing. The amount of mammals available to
feed on was limited, therefore the jaguars had to
adapt to eat reptiles.
What became the important adaptation?- the size
of their teeth and jaws.
The jaguars with the largest teeth and biggest jaws
could prey more easily on these hard shelled
reptiles, that when they had offspring, their
offspring inherited these traits. The descendents
showed modifications / changes over time.




Fossils
Geography / Biogeography
Embryology
Comparative Anatomy
Homologous Structures
 Analogous structures
 Vestigial structures





Person who studies fossils= Paleontologist
Defined as- the remains of plants and animals
that lived in the past.
Formed in sedimentary rock layers called
strata. The oldest are found in the deep rock
layers while the youngest or most recent
animals are found closer to the surface->
fossilized in sand, sediment, or volcanic ash.
Most fossils are found near aquatic / semi
aquatic regions.
Skeleton of
Basilosaurus isis
in Egypt. Lived 40
mya and had both
land and marine
characteristics.

Paleontology provides evidence to support evolution.

Two closely-related organisms will have similar
DNA sequences.


Where the plants and animals are found /
distributed around the world.
Try to figure out how similar groups of
organisms have dispersed to other places that
are separated by huge barriers like oceans.




The embryos / larval stage of individuals look
very similar to each other, but are drastically
different when they reach adulthood.
Fish, birds, reptiles, and mammals all have gill
slits as embryos.
In fish the gill slits become gills, mammals they
become ears and throats.
It is believed that the similarity in embryos in
very different organisms suggest that they all
evolved from a distant common ancestor.

Defined as the study of the structure of
living and fossilized animals and the
similarities (homologies) that indicate
evolutionarily close relationships.
Homologous structures
 Analogous structures
 Vestigial structures




Features that are similar in structure, different
in detail, but appear in different organisms and
have different functions.
Appearance across different species offers
strong evidence for common descent.
Ex- forelimb of a human, bat, and a mole.

In all of the animals the forelimbs have several bones
that are similar, but the same bones vary in different
animals.
Human hand
Human
Hand
Mole foot
Mole Foot
Bat wing
Bat Wing
The question is- If each of these groups descended from a
different ancestor, why would they share these homologous
structures?
They believe because they share a common ancestor.




They are considered homologous even though
the sizes of the bones are quite different in each
group- due to walking differently.
Humans, bears, raccoons, etc are plantigrades=
walk on their whole foot, from toe to heel.
Dogs and cats are digitigrades= only walk on
their toes.
Horses, cows, and deer are unguligrades= walk
on the very tips of their toes.


Organisms that evolved separately and are not
evidence of a common ancestor but have similar
structures that have similar functions.
Ex- Wings of a bat and the wings of insects.



Bats are mammals, insects are Gastropods
Bats have bones, insects wings have membranes
Function evolved separately but their ancestors faced
similar environmental challenges that led to these
structures.
Fly wing
Bat wing



Remnants of organs or structures that had a function
in an early ancestor but now serve no purpose or
function.
Ex- snakes have a tiny pelvic bone and stump like
limbs. Snakes share a common ancestor with
tetrapods such as lizards and dogs (considered
homologous structures).
Ex- Wings of ostriches. Use their wings for balance
but not to fly. Lost the function of their wings
because they learned to run fast and kick their
predators. The gene coding for large wings was not
preserved over generations.


Appendix in
humans->
remnants of the
cecum, part of the
large intestines in
plant eating
mammals.
Wisdom teeth in
humans. Why?
Vestigial organs such as the
pelvis and femur could
suggest that whales migrated
from land to sea.



https://www.youtube.com/watch?v=xCxnwkj8fU
https://www.youtube.com/watch?v=8cn0kf8
mhS4
https://www.youtube.com/watch?v=iIGo_5Q
IbxI
Genetic Variation
Natural Selection
Bottleneck & Founder effect
Hardy Weinberg Equilibrium
Speciation through Isolation
Extinction
A population shares a common gene pool.



Genetic variation leads to phenotypic (ex- body size
and feathers in penguins) variation.
Phenotypic variation is necessary for natural
selection (can be a large range from tall skinny
penguins to short fat penguins).
Genetic variation is stored in a population’s gene
pool.


Gene pool- the combined alleles of all the individuals in a
population. Different combos are caused from different
animals reproducing together.
Alleles= what your chromosomes are made of. Traits.

Allele frequencies measure genetic
variation.
– measures how common allele is in population
– can be calculated for each allele in gene pool


If brown skin color became more advantageous,
what would likely happen to the frequencies of
alleles G and g in this gene pool?
What does advantageous mean in this example?


The G allele would decrease and the g allele
would increase in frequency and become more
prevalent in the gene pool.
Advantageous means that the gene is more
“fit” therefore the chance of passing it onto its
offspring is great because it’s beneficial to the
species.

Mutation is a random change in the DNA of a gene.
– can form new allele
– can be passed on to
offspring if in
reproductive cells
• Recombination forms new combinations of alleles.
– usually occurs during meiosis
– parents’ alleles
arranged in new
ways in gametes

Hybridization is the crossing of two
different species.
occurs when individuals can’t find mate of
own species
 topic of current scientific research




Living among similar species
Can’t find a mate in their own species
Humans do it to better a product / make an
animal more interesting and marketable.
Natural Selection in Populations
Populations, not individuals, evolve.

A normal distribution graphs as a bell-shaped curve.
– highest frequency near
mean or middle value.
These phenotypes seem to
be the most common.
– frequencies decrease
toward each extreme
value being the least
favorable traits.
–Environmental conditions
can change and a certain
phenotype can become
advantageous (nature favors
this)

Microevolution is evolution within a population.

observable change in the allele frequencies over time.
can result from natural selection

There are three stages:

 1. Directional
 2. Stabilizing
 3. Disruptive selection



Causes a shift in a populations phenotypic
distribution. A phenotype that was once rare in
a population becomes more common.
Ex- Antibiotic resistance ( over 200 types of
bacteria have some sort of antibiotic resistance).
Ex- Ostriches speed and ability to kick
predators, octopus mimicking others, speed of
a cheetah, the jaws and teeth of a jaguar


The intermediate phenotype is favored
and becomes more common in the
population.
Ex- height- they are mostly average, not
too many that are tall and short.





Supports both extreme phenotypes while the intermediate are
selected against by something in nature.
Ex- Feather color in the male lazuli buntings. There are bright
blue headed adult males and young males that range from
dull brown to bright blue. Dominant adults have the brightest
blue heads and always get to choose their territory / first
choice with mates. The youngest males that are the brightest
blue and dullest brown win more mates than the males with
bluish brown feathers.
The adult, bright blue males are very aggressive towards the
young bright blues and bluish brown males that they see as a
threat, leaving the opportunity open for the dullest brown
intermediates to win over the mates because the others are too
busy fighting.
The bluish brown males are not as well adapted to compete
for mates because they are too blue to be left alone by the
aggressive adults and not blue enough to attract the females.
By favoring both phenotypes- bright blue adults and dullest
brown males could lead to speciation of the bright bluish
brown males.
KEY CONCEPT
Natural selection is not the only mechanism through which populations
evolve.




Gene flow- the movement of alleles from one
population to another.
Gene flow occurs when individuals join new
populations and reproduce.
Increases genetic variation of the receiving
population and keeps the neighboring populations
similar.
Low gene flow increases the chance that two
populations will evolve into different species.

Bald Eagle- They are
hatched and banded
on the Gulf Coast of
Florida. Some of these
hatchlings will leave
the area once they
learn how to fly and
migrate North. These
eagles may be joining
a new population.



Fruit flies
Plants and fungi spores
Some think that hybridization is an example
because it creates a new species.

Coyotes and Red wolves






Changes in allele frequencies that are due to chance.
Causes a loss of genetic diversity in a population
The allele is eliminated
Most common in small populations.
Two processes: Bottleneck Effect and the Founder
Effect
Problems it causes:


Population loses genetic variation= populations will be less
likely to adapt.
Lethal alleles that are carried in the homozygous individual
may be carried by the heterozygous animal, and could
potentially become more common in the gene pool due to
chance alone.



Genetic drift that occurs after an event greatly
reduces the size of a population.
Ex- Overhunting of Northern elephant seals. They
were hunted to near extinction in the late 1800’s for
its blubber (used to make oil). Population went to
about 20-100 individuals, but since the males are
extremely territorial and fight for reproductive
rights, very few males actually passed their genes on
to the next generation.
Now the population is up around 100,000 , however
the genetic variability in the population is very low
because many alleles were completely lost during
this, therefore leading to complete removal from the
gene pool.


Genetic drift that occurs after a small number
of individuals colonize a new area.
Ex- Amish of Lancaster, Pa- have a high rate of
Ellis-van Crevald Syndrome (type of dwarfism
that is rare in other populations) and has
become more common in this specific
population of Amish people. This syndrome
has bee traced back to the founding couples of
the community.


Certain traits increase mating success.
Cost differs between sexes:
Males- produce many sperm continuously,
therefore each sperm has little value. Many
investments at little cost to them.
 Females- limited in the number of offspring
they can produce in each cycle. Each
investment is valuable and they want it to
turn out successful.



The cost to the female makes them very
picky about their mate.
There are two types of selection:


1. Intrasexual selection- males compete and the
winner gets to mate with the female. More
focused on physical and aggressive fighting
behavior. Ex- Bighorn sheep
2. Intersexual selection- males display traits that
attract the female. Usually a secondary sex
characteristic that tells the female they are
attractive and fit. Ex- male peacock fanning out
its tail.



Some traits may be linked with
genes for good health and
fertility.
Some males offer traits that say
he can be the better father and
defend his offspring from
predators.
Some traits become exaggerated
over time. Example- red air sacs
of the male frigate bird.





Male giraffes
Bighorn Sheep
Elephant seals
Moose
Elk




Peacock
Sage Grouse
Frog calls
Male guppies with
bright blue and orange
spots
KEY CONCEPT
Hardy-Weinberg equilibrium provides a framework for understanding
how populations evolve.


Biologists use models to study populations.
Hardy-Weinberg equilibrium is a type of model.

Genotype frequencies stay the same if five
conditions are met or at equilibrium:





very large population: no genetic drift
no emigration or immigration: no gene flow
no mutations: no new alleles added to gene pool
random mating:
no sexual selection
no natural selection:
all traits aid equally
in survival

Real populations rarely meet
all five conditions.


Real population data is
compared to a model.
Models are used to
studying how populations
evolve.

Predicted genotype frequencies are compared with
actual frequencies.

used for traits in simple dominant-recessive systems
– must know frequency of recessive homozygote's
p2 + 2pq + q2 = 1
"The Hardy-Weinberg
equation is based on
Mendelian genetics. It is
derived from a simple
Punnett square in which
p is the frequency of the
dominant allele and q is
the frequency of the
recessive allele."






1. Genetic Drift
2. Gene Flow
3. Mutation
4. Sexual Selection
5. Natural Selection
Evolution is continuous, although very slow to
the human eye, it is a response to changes. As
environments change they can either adapt or
face extinction.

Environments are constantly changing, which
changes what traits are adaptive.

No, because the females select mates based on
the size of their tails-> sexual selection is
occurring.
KEY CONCEPT
New species can arise when populations are isolated.

Populations become isolated when there is no
gene flow.



Isolated populations adapt to their own environments.
Genetic differences can add up over generations and in
time the two isolated population become more and
more genetically different.
Individuals may also start to behave and look
differently as well.

Reproductive isolation can occur between isolated
populations.
– members of different populations cannot mate
successfully with one another due to different
reproductive times or they are isolated by a barrier of
some sort that gives them different microhabitats.
– final step to becoming separate species
• Speciation is the rise of two or more species from one
existing species.

I breed
January to
March
Rana aurora and
Rana boylii breed
at different times.
I breed
March
to May

Rana aurora (Redlegged frog) breeds in
fast-moving,
ephemeral streams
(temporary), whereas
its relative Rana
catesbiana (Bullfrog)
breeds in permanent
ponds. (They also go
through
metamorphosis at
different rates.



Isolation caused by differences in courtship or
mating behaviors.
Could be through chemical scents (ex- panda),
courtship dances of birds (peacock), or songs
and vocalizations (frogs and birds).
Ex- over 2,000 species of fireflies are isolated
this way. Males and females produce flashes of
light to attract mates of their own species. One
species may emit a flash once every second,
while others emit a double flash every 5.5
seconds.



Peacock- the faster the shake and the
more eyespots= the more attractive
he is to her.
Long Tailed widow bird- the longer
the tail the better. Flies around the
grassland showing the females his
long tail.
Sticklebacks- females prefer males
that are able to produce frequent
body shakes during courtship. Leads
to increased nest fanning.






https://www.youtube.com/watch?v=gqsMTZQpmE
https://www.youtube.com/watch?v=WdnPQrqni
IE
https://www.youtube.com/watch?v=ZPFkmwo8
DQU
https://www.youtube.com/watch?v=6x4FJseTnJ
U
https://www.youtube.com/watch?v=fR7Dqf0vzz
Q
https://www.youtube.com/watch?v=-zpajerFI1w

Geographic Isolation
- physical barriers divide populations into two or more groups.
- Rivers, mountains, dried up lakebeds.
- Ex- the Isthmus of Panama created a barrier for many marine species=
prevented them from crossing between the Atlantic and Pacific Oceans.
- Eventually the populations became genetically different.
- Ex- Snapping Shrimp- they look identical, however when males and females
get together they snap at each other instead of courting. They refuse to mate
with each other, therefore they formed different species.



When timing prevents reproduction between
populations.
Reproduce at different times of the year /
season.
Ex- see the frog example from reproductive
isolation.
KEY CONCEPT
Evolution occurs in patterns.


Random events= mutations, genetic drift,
anything that can’t be predicted.
Natural Selection= not random because
individuals with traits that are better adapted
for their environment have a better chance of
surviving and reproducing than individuals
without these traits.




Different species must adapt to similar
environments.
Defined as- evolution toward similar
characteristics in unrelated species.
Ex- analogous structures such as wings on a
bird and insects.
Ex- dolphins and sharks have evolved similar
tail fins that help them propel through the
water even though they are separated by 300
million years.


Closely related species evolve in different
directions.
Ex- the kit fox and red fox- closely related but
grew up in different environments therefore
their appearances are different.


Red fox- lives in temperate forests and has a dark
reddish coat that allows it to hide from predators.
Kit fox- lives in the desert and has large ears for heat
regulation.
Red Fox
Kit Fox
Ancestor



Directional Selection- causes a shift in a
populations phenotype (physical make-up)
Convergent- a similar trait in unrelated species
is selected for because of a common need /
benefit the trait provides in a given
environment.
Divergent evolution- closely related species
that are in different environments increasingly
adapt to those differences with traits that are
advantageous for survival in their different
environments.


They are examples of convergent evolution.
They do not share a common ancestor and the
shells evolved as a means of protection from
predators.

Coevolution- two or more species evolve in response
to changes in each other.


Usually a specialized relationship – mutualistic
Ex- the ant and the acacia plant. The acacia plant is covered
with thorns that protect it from larger herbivores, but small
insects like caterpillars can get in there and eat the sweet
nectar which it produces. There is a species of stinging ants
that live inside the thorns and feed on the nectar. The ants
protect the plant by stinging any organism that comes close
and tries to eat the plant.



“Evolutionary arms race”= species respond to
pressure from the other through a better
adaptation over many generations.
Ex- plants that produce chemicals so organisms
don’t eat them. Natural selection favors organisms
that can overcome the effects of the chemicals.
Ex- thick shells and spines of murex snails are an
adaptive response to crabs preying on them. Crabs
have evolved to adapt by growing more powerful
claws that are strong enough to crack the shells.




Extinction is the elimination
of a species from Earth.
Usually happens when a
species can’t adapt to a
change in its environment.
Background Extinctions and
Mass Extinctions.
More than 90 % of all
animals that have lived on
Earth are extinct.
Iberian lynxI’m the most
endangered
animal in the
world.





Extinctions that occur continuously but at a
very low rate.
Part of the cycle of life on Earth.
Occur at the same rate as speciation
Usually only affect one or a few species in a
small area.
Caused by local changes in the environment
such as the introduction of a new predator or
low food supply.







More rare and intense
Often occur on the global level
Destroy many species, even families or orders
They are thought to occur suddenly in geologic time,
usually due to a catastrophic event like the Ice Age or an
asteroid.
Five Mass extinctions in the past 600 million years.
The most studied mass extinction, between the
Cretaceous and Paleocene periods about 65 million years
ago, killed off the dinosaurs and made room for
mammals to rapidly diversify and evolve
(www.nationalgeographic.com)
The causes are unsolved mysteries but they think that
they may have been caused from volcanic eruptions and
asteroids, global warming, mass floods, etc.

Fossils can form in several ways:
Permineralization
 Natural Casts
 Trace Fossils
 Amber Preserved Fossils
 Preserved Remains


Permineralization occurs when minerals carried by
water are deposited around a hard structure.

A natural cast forms when flowing water removes all
of the original tissue, leaving an impression.

Trace fossils record the activity of an organism.

Amber-preserved fossils are organisms that become
trapped in tree resin that hardens after the tree is buried.

Preserved remains form when an entire organism
becomes encased in material such as ice or volcanic ash.

Specific conditions are needed for fossilization.
• Only a tiny percentage of living things became
fossils.

Relative dating
estimates the time
during which an
organism lived.


It compares the
placement
of fossils in layers of
rock.
Scientists infer the
order in
which species
existed.

Radiometric dating uses decay of unstable isotopes.
– Isotopes are atoms of an element that differ in their number of
neutrons.
neutrons
protrons
• Radiometric dating uses decay of unstable
isotopes.
– Isotopes are atoms of an element that differ in their number of neutrons.
– A half-life is the amount of time it takes for half of the isotope to decay.

Index fossils can provide the relative age of a rock layer.



existed only during specific spans of time
occurred in large geographic areas
Index fossils include fusulinids and trilobites.
Geological Time Scale
Organisms
Cenozoic Era- Recent Life
Quaternary
Includes all present life forms
Tertiary
Mammals, flowering plants, grasslands, insects, fishes,
and birds became more diversified. Primates evolved.
Mesozoic Era
Cretaceous (Major Extinction)
Dinosaurs peaked and went extinct, birds survived and
flowering plants arose.
Jurassic
Dinosaurs diversified as well as early trees that are
common today. Oceans were full of squid and fish.
First birds arose.
Triassic (Major Extinction)
Following the largest mass extinction, dinosaurs
evolved, ferns and cycads evolved, and mammals and
flying reptiles arose.
Paleozoic Era- Ancient Life
Permian (Largest Mass Extinction)
Modern pine trees arose and Pangaea was formed
Carboniferous
Coal forming sediments were laid down in swamps,
fish continued to diversify, amphibians, insects, and
small reptiles were around,
Devonian (Major Extinction)
Fish diversified. First sharks, amphibians, and insects
showed up. First trees and forests arose.
Silurian
Earliest plants arose, glaciers melted and seas formed,
and jawless and freshwater fishes evolved.
Ordovician (Major Extinction)
Diverse marine invertebrates and early vertebrates.



Multicellular organisms
first appeared during the
Paleozoic era.
The era began 544 million
years ago and ended 248
million years ago.
The Cambrian explosion led
to a huge diversity of
animal species. All life was
found in the ocean.
• Life moved onto land in the middle of the
Paleozoic era.



The Mesozoic era is known as the Age of Reptiles.
It began 248 million years ago and ended 65 million
years ago.
Dinosaurs, birds, flowering plants, and first
mammals appeared.


•
The Cenozoic era began 65 million years ago and
continues today.
Placental mammals and monotremes evolved and
diversified.
Anatomically modern humans appeared late in the era.