Unit 2- Evolution for Biology 2015 November 2nd

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 its paddle shaped feet for burrowing,
and 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.
 Why does it need to eat that fast?
 How
do these traits arise in the
first place?
 Mutations
that have been passed
down from generation to
 What
other factors could have
contributed to the star nosed
moles distinctive features over
› 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
 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
Group of the same species that live in
the same area at the same time. They
share unique set of genes.
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
(sex cells= sperm and eggs) 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.
 1.
Catastrophism- sudden, natural disasters
such as floods and volcanic eruptions
have happened often during history and
have shaped landforms -> caused species
to become extinct.
 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,
and floods =
Mass Extinctions.
 Canyons
carved by
rivers show
occur in small
steps over
Rock strata demonstrates the geological
processes, which over time shows great
 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
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
 1 species turned into 14 different
 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
 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=FT3FU2XOgo&feature=bf_prev&list=PL8D
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
 1. What traits in the sea lion population
might be adaptive?
 2. How would the population change?
Streamlined body
allows them to swim
fast and efficiently.
 Powerful flippers
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.
 Artificial
Selection & Heritability
 Struggle to survive
 Natural Selection
 Darwin
was convinced evolution
could occur, but he couldn’t
explain how.
 He spent more than 20 years
researching and eventually
turned to farmers and breeders
for help.
 Humans
change a species by
breeding it for certain traits.
neck feathers
tail feathers
Darwin noticed a lot of variation in
domesticated animals and plants. More so
than in wild populations. He saw that
breeders could take certain traits and
produce diversity in an organism.
Humans determine which traits are
favorable and breed those individuals
that show those traits.
neck feathers
tail feathers
In order for artificial-natural selection to
occur, the trait has to be passed down
from one generation to another=
Ability of a trait to be passed down from
one generation to the next.
 Key factor in making artificial selection
› Darwin tried to compare
adaptation with breeding.
Breeders wanted reversed neck
feathers, inflatable crops, tail
feathers, etc. Breeders also
selected against traits that they
felt were not favorable.
› In artificial selection, humans are
the selective agent.
› In nature, the environment is the
selective agent.
Individuals that have inherited beneficial
adaptations produce more offspring on
average than do other individuals.
 Nature: characteristics are selected only
if they give the individual an advantage.
› Darwin came up with the Theory of Natural
Selection after reading Malthus’ essays.
› Thomas Malthus: food, water, and shelter were
natural limits to population growth.
 Example: Human population would grow
geometrically if we had unlimited resourcesdisease and limited food kept populations smaller
(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
Resources can’t keep up, therefore things / factors such
as poverty, wars, plagues, and famines begin to
influence populations.
If resources are limited and organisms have
more offspring than could survive, why do
some organisms survive and others die?
All the individuals of a species living
Some had variations that were well
suited for the environment in which it
 Darwin proposed that changes occur
over many years / generations=
Darwin wasn’t alone, Alfred Wallace also
proposed similar findings, and the two
collaborated (28 years later, Darwin
published Origin of Species).
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.
› Mutation: a permanent change in the
nucleotide sequence of the genome of an
 Producing
lots of offspring at one time.
Increasing the chances of survival.
 Ex- Sea turtle: clutch of 100 eggs, 5
may grow into adults. They can die off
due to competition between offspring
and other environmental conditions.
 Certain
variation allows others
to survive better than others.
Successful individuals live
longer, produce more
offspring, and pass on good
Species with adaptations that are well
suited for reproduction and survival will
continue to pass along the traits and
more individuals will carry them= very
successful as long as the environmental
conditions favor that trait.
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 and 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.
1. Acts on phenotypes, physical characteristics not
› Phenotypes: physical characteristics such as claws, brown
eyes, camouflage color, etc.
› Genotype: genetic make-up that determines the
2. New alleles are not made they occur by mutations.
› Alleles: one of two or more versions of a gene. An individual
inherits two alleles for each gene, one from each parent. If
the two alleles are the same, the individual is homozygous
for that gene. If the alleles are different, the individual is
3. Can only act on traits that are all ready there.
› Trait: genetically determined condition. They can be
physical or behavioral. Physical such as hair color,
behavioral such as nesting in birds.
1977- in the Galapagos there was a drought
that wiped away the small, soft seeds that the
finches favored, leaving behind lots of large,
shelled seeds. The large beaked population
increased and the small beaked finches died.
 1984- There was an unusual wet period that
decreased the large seeds, which favored
the small seeds, increased the smaller finches,
and decreased the population of larger
 Fossils
 Geography
/ Biogeography
 Embryology
 Comparative
› 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.
 Fossils support Darwin’s concept of descent with
Transitional fossils are important in linking where one
group ends and another begins.
› Ex- Basilosaurus
Age fossils by using Absolute/Radioactive dating.
› Uses specific radioactive atoms and how fast they break
down to date the rock they are found in.
Relative dating Uses the “Law of Superposition” to
figure out how old an object is based on placement
in rocks. Oldest rocks on bottom youngest on top.
Geologic Time Scale- Picture of when things
appeared on Earth.
Skeleton of
Basilosaurus isis
in Egypt. Lived
40 mya and had
both land and
Paleontology provides evidence to support evolution.
› Darwin proposed that species closely resemble
the species that reside on the nearest mainland
and that somehow they migrated.
› Each island had different ecosystems with
different plants, climates, and predators.
› Over time, the traits became established on the
islands mainly due to the fact that the mainland
population was too far away.
 Ex- finches
› Biogeography- study of the distribution of
organisms around the world or comparing
similar species in different parts of the world. It
tells us how organisms migrate and evolve into
new species.
The embryos / larval stage of individuals
look very similar to each other, but are
drastically different when they reach
 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
 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 function.
› What is the function of a human hand, a bat
wing, and a mole foot?
Human hand
Mole foot
Mole Foot
Bat wing
Bat Wing
If each of these groups descended from a different
ancestor, why would they share these homologous
They believe because they share a common ancestor.
Organisms that evolved separately, no
common ancestor, made up of different
structures, but have similar functions.
 Ex- Wings of a bat and the wings of insects.
› Bats are vertebrates, insects are invertebrates
› Bats have bones, insects wings have
› 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
remnants of the
cecum, part of
the large
intestines in
plant eating
 Wisdom teeth
in humans.
Vestigial organs such as the
pelvis and femur could
suggest that whales
migrated from land to sea.
 https://www.youtube.com/watch?v=8c
Molecular and genetic evidence
support fossil and anatomical evidence.
 Let’s look at the basics of DNA and
Proteins before diving in 
All living things have DNA.
 Shape looks like a twisted ladder /
double helix
 Detailed instructions that build proteins
and are stored in extremely long carbon
based molecules.
Nucleotides are made up of: sugar,
phosphate group, and a nitrogenous base
(adenine, thymine, guanine, and cytosine).
Nitrogenous bases always pair up in the
same way!!!
For DNA: A binds with T & C binds with G
For RNA: A binds with U & C binds with G
In RNA, thymine is replaced with uracil
Two types: DNA and RNA
DNA and RNA work together to make
proteins. DNA passes on genetic
instructions to RNA. RNA decodes and
turns the genetic information into a
 DNA is the basis of genes and heredity.
Amino acids are referred to as the “building
blocks” of proteins and are thought to be the
first molecules on Earth.
 We use 20 different amino acids to build
proteins in our bodies.
 Your body makes 12 and the others need to
be ingested through meat, beans, and nuts.
 Functions: speed up reactions in the body
(enzymes), defensive proteins, storage
proteins, transport proteins, support proteins,
motion proteins, and messenger proteins.
* Sequences of nucleotides (sugar,
phosphate, and nitrogenous base) in a gene
change over time because of mutations.
* This analysis allows us to look at organisms
DNA. The more similar their DNA is to each
other, the closer they are related.
Like vestigial structures. They are riding
along with the other functional DNA, but
they have no function.
 They do have the ability to change as
they get passed on from generation to
Control the development of specific
 Have been found in organisms from fruit
flies to humans = common ancestor
 Have been found in organisms as far
back as 600 million years ago.
Comparing their proteins = “molecular
 Sets of proteins that are unique to
specific muscle and liver cells.
 Example- Proteins found in ancient
marine worms were found to closely
resemble those of cells found in the
vertebrate eye.