Transcript Evolution notes

EVOLUTION
Taxonomy
• Taxonomy— is the science of classifying and naming living
things.
• How are relationships between living things determined?
They are determined by:
• 1. Physical Similarities— ex: structure (bones)
• 2. Chemical Similarities— ex: DNA
• 3. Behavior— ex: mating and survival strategies
How are living things classified?
Binomial nomenclature- each species is assigned a two-part
scientific name. This system includes seven levels or taxa.
King
Philip
Came
Over
For
Good
Soup
Why is it important for scientists to have a universal
classification & naming system?
• To avoid confusion caused by the use of different
common names, language barriers, & cultural
barriers.
Species— A group of
organisms that can mate
• They use scientific names
and produce fertile
offspring.
.
• According to Linnaeus’ system, every species has a Latin scientific
name composed of the genus and species names. The first letter of
the Genus is always capitalized. The first letter of the species is
lowercase. The entire scientific name is italicized or underlined
1. Which 2 organisms are the most closely related? Cat & Lion
2. Which organism is least similar to the others? Human
Key : A= Human
B= Cat
C= Lion
D= Dog
3. What is the scientific name for a cat? Felis domesticus
A dog? Canis familiaris
A lion? Panthera leo
Explain:
• Scientific names of species of organisms consist of
two names.
• What two taxa (levels) are used to compose the
scientific name & why these two?
The Genus and species are
used; because they are most
specific
Diversity
• Diversity: The number of different species in an
ecosystem.
• Why is a more diverse ecosystem more stable?
• There is more than one type of organism to fill a role (producer,
predator, prey, etc.), so if one disappears, there is a “back up”.
• Example:
An ecosystem with one producer will
fall apart, if that species goes extinct.
Evaluate
• Many species of plants and animals are currently
threatened or in danger of extinction.
• (1) How does extinction affect biological diversity?
Biological diversity decreases
• (2) What kind of long-term effects do you think the
extinction of other species can have on our lives?
Extinction sometimes allows for other
organisms to take over an area. Biodiversity will
decrease, but new organisms could evolve.
Phylogeny
• Phylogeny: an organism’s evolutionary history. An
organism’s phylogeny can be diagramed using a
phylogenetic tree. A phylogenetic tree is a branching
diagram that shows evolutionary relationships.
Common Ancestor
Common Ancestor— A
•species
Scientists classify
organisms
based on their
from
which
two
similarities in DNA, anatomy, and behavior.
or more species are
directly descended from.
• How is the phylogeny of an organism determined?
Apply
Examine the phylogenetic tree to answer the
following questions:
1. Which organism is most closely related to a
flowering plant? Fern
2. Which organism is the most primitive (oldest)? Protista
3. What kingdom is the common ancestor of all these
plants? Protista
Apply
Apply
1. What animal is most closely related to a bird? Crocodile
2. What animal is most closely related to a lizard? Snakes
3. Is a mammal more closely related to a turtle or a shark? Turtle
4. Is a shark more closely related to an amphibian or a turtle?
Amphibian
5. Is a crocodile more closely related to a lizard or a turtle? Lizard
Explain
• (1) How do you determine which organisms on a
phylogenetic tree are the most closely related?
Their branches are closely traced.
• (2) Least related?
Their branches are far apart or are separated.
• (3) How do you determine which organism on the
phylogenetic tree is the common ancestor?
The organism where all of the other branches
originate.
Evolution and Darwin’s Theory
• Evolution: change in inherited traits over time.
Why Should We Study Evolution?
• It helps us understand relationships between
species in ecosystems.
• It also explains the development of antibiotic
resistance in bacteria and insecticide
resistance in bugs.
Why Should We Study Evolution?
• Understanding relationships between organisms can
help us make conclusions in medical research.
• E.g.: It explains how HIV and influenza can change
(mutate).
Darwin’s Theory
• Darwin’s Theory: In 1859 Darwin combined his
observations of living plants, animals, and
fossils from around the world, and developed
his theory of evolution, which today is the most
accepted scientific theory to explain
biodiversity.
• Species Change through Natural Selection
Natural Selection
• The most important influence on evolution is natural
selection, which occurs when an organism is subject
to its environment.
• The ‘fittest’ or ‘best’ organisms survive and inherit
their genes to their offspring, producing a population
that is better adapted to the environment. The genes
of less-fit individuals are eventually lost. The
important selective force in natural selection is the
environment.
•RESTATE the above in your own words at the
top of page 5.
Factor that Affect Natural Selection
• I. Genetic variation: All species have natural genetic
variation as a result of random mutation.
• Variation: Genetic diversity, changes within a
species.
Variation within a species can be caused by:
• a. Mutation: DNA changes during replication
• b. Crossing-over: The exchange of genetic material
between homologous chromosomes.
Factor that Affect Natural Selection
• Selective environmental pressures: The environment
presents challenges to survival. Organisms sustain
their populations by producing more offspring than
can survive.
• Examples:
Predator-prey interactions, resource shortage,
changes in environmental conditions.
Factor that Affect Natural Selection
• Competition: There is a struggle for survival. The
fittest individuals (those whose genes give them an
advantage) will be able to survive.
• Examples: Trees with bitter sap are less appetizing to
herbivores than sweeter trees, and therefore survive
better than other trees.
Factor that Affect Natural Selection
• Adaptation: Any variation in the traits that allows an
organism to survive and reproduce successfully is
inherited to its offspring. Over generations, these
traits become more common in the population as the
population adapts to its environment.
• Examples: Resistance to toxins; camouflage; ability
to conserve water; antibiotic resistance.
Factor that Affect Natural Selection
• Susceptibility: Individuals (and species) that are not
able to survive and reproduce will become more
susceptible to extinction (die off).
• Their traits/genes will become extinct with them.
• [Susceptible = Likely to be affected]
• Examples of extinction: Javan tiger
Organisms who can’t adapt
Variation
Susceptibility
Competition/enviro
pressure
Adaptation
Competition/
adaptation
• What do we call a change in the DNA?
Mutation
• How can natural selection increase diversity?
Natural selection provides a way for new species to
evolve, which can increase diversity.
Are the fittest individuals the same in all
environments?
No; in different environments, different traits will
provide an advantage.
Summary (pg. 7)
• What were the variations in the ‘organisms’ in the
“Quackers” lab? Color = light or dark colored quackers
• What was the selective pressure in the “Quackers” lab?
Predation
• Were you a predator or prey in the “Quackers” lab?
Predator
• Could little variation in a species cause an organism to
die off (become extinct)? Why or why not?
Yes, if there is little variation within a species they may not be
able to adapt well to any changes in their environment.
• In the African savannah there used to be only short-necked giraffes.
The environment was green and lush, but a severe drought started.
Plants were less available, and there was more competition. After
several generations, the giraffe population included long-necked
giraffes in addition to short-necked giraffes. Many years later, longnecked giraffes were more prevalent than short-necked giraffes.
• • What are the variations in the giraffes?
• • What is the selective pressure?
Neck length
Competition
• • Which group of giraffes is the most fit in the new environment?
Long Neck
• • Which group of giraffes is the most susceptible to extinction?
Those with short necks
Explain
• EXPLAIN: In the ‘Apply’ scenario on the previous page, how did the
long- necked giraffes appear in the population?
• Why are all current giraffes long-necked?
Evidence that Supports Evolution
• I. Physiological Adaptations: Changes in organism’s
metabolic processes.
• Examples: Bacteria developing antibiotic resistance.
Evidence that Supports Evolution
• II. Biogeography: The study of the distribution of
living organisms through space and time on Earth.
Biogeography looks at current species of living
organisms, as well as at the evidence of past life
(fossils), in order to determine how species arose.
Evidence that Supports Evolution
• III. Fossils: Any evidence of an organism that lived
long ago.
• Most fossils form in sedimentary rock. This type of
rock is formed when sediments (sand, pieces of rock)
form layers and is compressed together.
• Organic matter trapped between the layers decays
slowly and a fossil isleft behind.
• Examples: Footprints, pieces of bone….
Evidence that Supports Evolution
• How do fossils show evidence of evolution?
They can show us what organisms looked like
in the past, and we can trace how they
change over time.
Evidence that Supports Evolution
• SUMMARY: The diagram represents different layers
of soil. The letters represent fossils of three different
species of organisms.
• 1. Which species is most likely oldest?
C- at the bottom
• 2. Which species most likely existed at the same time?
A&B, A&C – in the same rock layer
Evidence that Supports Evolution
• Embryology: The study of the early development of
an organism.
• How does embryology show
evidence of evolution?
Organisms who share embryological
similarities are probably related (share a
common ancestor).
Evidence that Supports Evolution
• V. Biochemistry: Nearly all organisms share DNA, ATP,
and many enzymes among their biochemical
molecules. The more closely related organisms are, the
more similar their DNA (and therefore, proteins) will
be.
• Example: The enzyme cytochrome c, occurs in
organisms as diverse as bacteria and bison. Biologists
compared the differences in the amino acid sequence
of cytochrome c that exist among various species.
Species that are most closely related to each other
have fewer differences in their amino acid sequences.
Evidence that Supports Evolution
• Example 2:The table shows the results of gel electrophoresis.
DNA has been cut into pieces… the smaller pieces move
further down the tray. By comparing DNA we can determine
who is more closely related.
• Which species of deer are most closely
related?
1&3 – the most matching
bands of DNA
Evidence that Supports Evolution
• APPLY: Bonobo blood has a protein with the sequence of
amino acids shown in the figure. This protein, hemoglobin,
carries oxygen in bonobo blood. Hemoglobin is also found in
human blood. What does this say about the relatedness
between humans and bonobos?
That they are
related or have a
common
ancestor.
Evidence that Supports Evolution
• VI. Homologous Structures: structures found in
organisms with a common evolutionary history.
Examples: Bat
wings, whale
fins, and human
arms all have
similar bone
structure and
are all mammals
.
Evidence that Supports Evolution
• How do homologous structures show evidence of
evolution?
If two organisms have homologous
structures they are related and have come
from a common ancestor.
Evidence that Supports Evolution
• VII. Vestigial Structures: Structures that have a
reduced (or no) use in an organism, but might have
had a larger use in an ancestral species.
• Examples: Human tail bone, whale pelvis bone, snake
leg bones, nictitating membrane in the eye.
Evidence that Supports Evolution
• How do vestigial organs show evidence of evolution?
They indicate a structural history.
Vestigial
Structure
Homologous
structure/fossils
Biogeography
Homologous
structure
Embryology
Biochemistry
• Could too little variation cause it to become extinct?
• Why or why not?
Yes; if there is little variation within a species, the
populations may not be able to adapt well to any
changes in their environment.
Genetics of Natural Selection
• Natural selection changes the frequency of certain
genes within a population over time as the
population adapts to its environment.
• Evolution works at the POPULATION level, NOT the
individual level.
• Gene Pool—The entire collection of genes among a
population.
Genetics of Natural Selection
• Gene Flow (also known as gene migration)- It is the
transfer of alleles of genes from one population to
another.
• Example: When the migrating individuals interbreed
with the new population, they contribute their genes
to the gene pool of the local population. This
establishes gene flow in the population. Gene flow
occurs, for example, when wind carries seeds far
beyond the bounds of the parent plant population.
Genetics of Natural Selection
• Genetic Drift- It occurs when a small group of
individuals leaves a population and establishes a new
one in a geographically isolated region.
• For example, when a small population of fish is
placed in a lake, the fish population will evolve into
one that is different from the original. Fitness of a
population is not considered in genetic drift, nor does
genetic drift occur in a very large population.
Genetics of Natural Selection
• Allelic Frequency: The percentage of a particular
allele (gene version) within a gene pool; it can
increase or decrease. Allelic frequencies can be
affected by two types of DNA changes: replication &
crossing over.
• If an organism survives in their environment they are
able to reproduce and pass on their genes to their
offspring. This will increase their alleles in the
population.
• APPLY: In certain cattle, red hair (R) is dominant to
white hair (r). Heterozygous (Rr) cattle are ‘roan’ in
color and have both red and white hair. What would
happen to the allelic frequency of the (r) allele if
coyotes noticed the white calves more easily?
The percentage of the r allele would decrease in
the population.
Gradualism vs. Punctuated Equilibrium
Darwin's theory included the fact that evolutionary changes take
place slowly. In many cases, the fossil record shows that a species
changed gradually over time. The theory that evolution occurs
gradually is known as gradualism. In contrast to gradualism is the
theory of punctuated equilibrium, which is a point of discussion
among scientists. According to the theory of punctuated equilibrium,
some species have long, stable periods of existence interrupted by
relatively brief periods of rapid change.
• Both groups of scientists agree that natural selection is the single
most important factor in evolutionary changes in species. Whether
the change is slow and gradual, or punctuated and rapid, one thing
is certain: Organisms have evolved over time.
• EVALUATE: After reading the passage above, briefly
discuss below (in writing) which of the two theories
(gradualism or punctuated equilibrium) you think is
best supported by current evidence, and why you
think so.
Behavior
• Behavior: How an organism reacts to changes in its
internal and external environment.
• What is the effect of natural selection on behavior?
Behaviors will be maintained or removed based on
their overall contribution to the fitness of an
individual. The behavior must be genetic because
selection changes the frequency of that gene (alleles)
in the gene pool.
• Animals display various behaviors for many reasons.
Generally, behaviors can be linked to a goal of survival or
reproduction. One famous biologist, Niko Tinbergen, noticed
that Common Black-headed Gulls would meticulously remove
the eggshell fragments from their nests after their offspring
hatched. In an attempt to understand this behavior, he
painted chicken eggs so that they were camouflaged into the
backgrounds where the gulls lived and nested. He then placed
some broken eggshells near them. He then noted how many
eggs were discovered and eaten by Carrion crows. He
observed that crows were able to easily notice the white
interiors of the broken shells and consumed many more of the
camouflaged eggs near the broken shells than camouflaged
eggs with no broken shells near them.
• Draw the two nests from the example in the passage
• 1. What question was Tinbergen attempting to answer with his
experiment?
• 2. Why did Tinbergen set up one area with camouflaged eggs and
no shell fragments?
• 3. In your opinion, why do the gulls behave this way?
• 4. Is the behavior learned or inherited?
• 5. How is the behavior of the gulls linked to natural selection?
Speciation
• Speciation: The evolution of a new species from old species.
• How can you tell members of two different species apart?
• By physical characteristics, DNA, and behavior.
• What is a species?
• A group of organisms that can mate and produce
fertile offspring.
Speciation
• How can natural selection produce a new species?
• 1. Natural selection causes changes in allelic frequency of a
population.
• 2. Different parts of a population might change in different ways.
• 3. Due to these changes, the 2 parts of the population are now
unable to mate.
• 4. If the two parts can no longer mate this means a new species
has evolved.
Speciation
• Reproductive Barrier: Any factor that prevents fertile
offspring from being produced.
• Examples of Reproductive Barriers:
• Geographical Barriers: Rivers, mountains, canyons,
etc.
• Temporal (Time) Barriers: Species do not mate at the
same time.
Different Sides of Explanation
• When evaluating the validity of a proposed
explanation of a biological phenomenon, one should
remain objective and ask oneself questions such as:
• − Is the reasoning relevant and sufficient?
• − Is the explanation supported by data?
• − Has relevant information been omitted?
• There is compelling evidence that mitochondria and chloroplasts
were once primitive bacterial cells. This evidence is described in the
endosymbiotic theory. What does that name mean? Symbiosis
occurs when two different species benefit from living and working
together. When one organism actually lives inside the other it’s
called endosymbiosis. The endosymbiotic theory describes how a
large host cell and ingested bacteria easily become dependent on
one another for survival, resulting in a permanent relationship.
Over millions of years of evolution, mitochondria and chloroplasts
have become more specialized and today they cannot live outside
the cell.
• Mitochondria and chloroplasts have striking similarities to bacterial
cells. They have their own DNA, which is separate from the DNA
found in the nucleus of the cell. Both organelles use their DNA to
produce enzymes and other proteins required for their function.
The two organelles also reproduce like bacteria, replicating their
DNA and directing their division.
• READING COMPREHENSION: After reading the
paragraph about the endosymbiotic theory (previous
page), and based on what you know about the
function of cell organelles, answer the following
questions.
Mitochondria
• ______________
are the result of endocytosis of
aerobic bacteria.
Chloroplasts
• ______________
are the result of endocytosis of
photosynthetic bacteria.
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