Transcript Regents Biology Regents Biology Vestigial organs Structures of

What is Evolution?



Change over time
The theory of evolution proposes that
modern forms of life have descended from
earlier forms of life and changed as they
descended.
What caused the “changes” or differences
in traits?

MUTATIONS!!

Can we control this?
Why is the Theory of Evolution so
Controversial?


People have varying beliefs on the origin
of life due to religion.
Biological evolution does not study the
origin of life. It only studies the changes
in life forms since their origin.
Mechanisms that drive evolution?
Mutation= random changes in the DNA
 Natural Selection
 Gene Flow= movement of alleles into or out of
a population
 Genetic drift= changes in the alleles of a
population due to random events (i.e. natural
disaster.
Important terms to know:
• adaptation- A characteristic that increases
fitness.
• fitness- The ability to survive.

What is natural selection?



A theory introduced by Charles Darwin
A process that increases or decreases the
presence of a trait depending on the
trait’s ability to keep the organism alive
and reproducing.
3 conditions must be met for natural
selection to occur:



Variation in characteristics (due to
mutations)
Differences in fitness
Heritability (can be passed down to
offspring) of the characteristic
Examples of Natural Selection
Galapagos finches= different beaks
 Male peacocks= varying brightness in
their feathers
 Giraffes= varying neck length
 Sharks= white on the underside and
blue/gray on top
 Humans= varying resistance to malaria
 Bacteria= antibiotic resistance

Natural Selection Lab
Natural Selection Lab
How do we know if evolution has occurred?
 The Hardy-Weinberg Principle calculates
genetic variety in a population. If the
genetic variety remains constant from one
generation to the next, it is said to be in
Hardy-Weinberg equilibrium (not
evolving).

The H-W equation is:
q2 + 2pq + p2= 1 (or 100%)
Hardy-Weinberg continued…
q2= the frequency of homozygous
recessive individuals.
2pq = the frequency of heterozygous
individuals.
p2= the frequency of homozygous
dominant individuals.
Hardy-Weinberg Goldfish Lab
Evidence of Common Ancestry
The theory of evolution states that all
living things have descended from another
life form, just as you have descended
from your parents and they descended
from their parents.
 The evidence that supports this theory
includes:

Fossils
 DNA
 Embryo structure
 Comparative anatomy

Cladogram
Evolutionary relatedness between
organisms can be demonstrated on a
diagram called a cladogram.
 Organisms with similar characteristics
are placed more closely on the diagram
because they are thought to have
evolved more closely to one another.
 As an organism evolves, there is a new
branch on the cladogram.
 Characteristics that evolve between
species are called derived characters.

Insect Cladogram Activity
Insect Cladogram Activity
Evidence of Common AncestryFossil Record
 Layers of rock contain fossils

new layers cover older ones
 creates a fossil record over time

fossils show a series of organisms that
have lived on Earth
Regents Biology
Evolution from sea to land
 Fossils are also evidence of transitional (in
between) forms.
 In 2006, there was the fossil discovery of the
missing link between sea and land animals


4 limbs
called Tiktaalik
Regents Biology
Evidence of Common AncestryComparative Anatomy
Animals with different
structures on the surface
But when you look under
the skin…
It tells an evolutionary story
of common ancestors
Regents Biology
Compare the bones
 Limbs of different animals that perform
different functions are built with the
same bone structure
How could these
very different animals
have the
same bones?
Regents Biology
Homologous structures
 Structures that come from the same origin
 homo = same
 logous = information
 Forelimbs of humans, cats, whales, & bats
are homologous structures.
same internal structure but different
functions
 evidence of common ancestor
 The greater the # of homologous
structures between organisms, the more
closely related they are.
Regents Biology

But don’t be fooled by these…
 Analogous structures
look similar on the outside
 have the same function
 different internal structure
 This means they do not have a close
evolutionary relationship
How is a bird

like a bug?
Regents Biology
Regents Biology
Vestigial organs
 Structures of modern animals that have
no function
evolutionists believe that these were
functional in ancestors
 evidence of change over time

 some snakes & whales have pelvis bones &
leg bones of walking ancestors
 eyes on blind
cave fish
 human tail bone
Regents Biology
Vestigial organs
 Hind leg bones on whale fossils
Why would whales
have pelvis & leg
bones if they were
always sea creatures?
Because they
used to
walk on land!
Regents Biology
Evidence of Common AncestryEmbryology
 Development of an embryo tells an
evolutionary story

The greater the # of similar structures
during embryo development, the more
closely related they are.
Regents Biology
Regents Biology
Evidence of Common AncestryBiochemistry
 Comparing DNA & protein structure

Every living thing uses the same
genetic code!
Human
Macaque
Dog Bird
Frog
Lamprey
8
32 45
67
125
 The fewer the number of
differences in the amino
acid sequence of common
proteins, the more closely
related organisms are.
number of amino acids different
from
human
hemoglobin
Regents
Biology
0 10 20 30 40 50 60 70 80 90 100 110 120
Horse
Chicken
Tuna
Frog
Shark
Turtle
Monkey
Rabbit
Human
6
6
9
8
14
8
1
4
Rabbit
5
5
9
6
12
7
5
X
Monkey
7
8
10
8
13
9
X
X
Turtle
7
2
9
5
12
X
X
X
Shark
11
12
12
12
X
X
X
X
Frog
8
3
8
X
X
X
X
X
Tuna
11
7
X
X
X
X
X
X
Chicken
7
X
X
X
X
X
X
X
•What 2 organisms on the chart above are the most alike in terms of DNA?
•What 2 organisms are the least alike?
•What is the turtle’s closest relative? Why does this data make sense?
Regents Biology
What data from whole
genome sequencing can tell
us about evolution of humans
Regents Biology
Example: the
Evolutionary Hypothesis
of Common Ancestry
Chromosome Numbers in
the great apes:
human (Homo)
chimpanzee (Pan)
gorilla (Gorilla)
orangutan (Pogo)
46
48
48
48
Testable prediction:
If these organisms share a common
ancestor, that ancestor had either
48 chromosomes (24 pairs) or
46 (23 pairs).
Regents Biology
Ancestral
Chromosomes
Chromosome Numbers in
the great apes
(Hominidae):
human (Homo)
chimpanzee (Pan)
gorilla (Gorilla)
orangutan (Pogo)
Fusion
Homo sapiens
Inactivated
centromere
46
48
48
48
Telomere
sequences
Centromere
Telomere
Testable prediction:
Common ancestor had 48 chromosomes (24 pairs) and
humans carry a fused chromosome; or ancestor had 23
pairs, and apes carry a split chromosome.
Regents Biology
Human Chromosome #2 shows the exact
point at which this fusion took place
Homo sapiens
Inactivated
centromere
Telomere
sequences
Chr 2
“Chromosome 2 is unique to the human lineage of
evolution, having emerged as a result of head-tohead fusion of two acrocentric chromosomes that
remained separate in other primates. The precise
fusion site has been located in 2q13–2q14.1 (ref.
2; hg 16:114455823 – 114455838), where our
analysis confirmed the presence of multiple
subtelomeric duplications to chromosomes 1, 5, 8,
9, 10, 12, 19, 21 and 22 (Fig. 3; Supplementary
Fig. 3a, region A). During the formation of human
chromosome 2, one of the two centromeres
became inactivated (2q21, which corresponds to
the centromere from chimp chromosome 13) and
the centromeric structure quickly deterioriated
(42).”
Hillier et al (2005) “Generation and Annotation of the DNA
sequences of human chromosomes 2 and 4,” Nature 434: 724 – 731.
Regents Biology
Building “family” trees
Evolution evidence can be used to create family
trees. Closely related species are branches on the
tree — coming from a common ancestor
Regents Biology
Human Impact on EvolutionSelective Breeding
Humans create the
change over time
Regents Biology
“descendants”
of the wolf
Artificial Selection
…and the
examples
keep coming!
I liked
breeding
pigeons!
Regents Biology
Insecticide resistance
 Human activities like spraying crop
fields with insecticides leads to:
The survival of insects that are
resistant to the insecticide
 Resistant survivors reproduce
 Resistance is inherited
 Insecticide becomes less & less
effective

Regents Biology
Regents Biology