Download Natural Selection Notes - West Branch Local School District

Evolution

Darwin:



HMS Beagle
Galapagos Islands
Artificial Selection-breeding to produce offspring
with desired traits-He inferred that if humans could
change species (animals or crops) by artificial
selection, then over time this process could produce
new species.



Patterns of
Diversity were
shown
Unique
Adaptations in
organisms
Species Not Evenly
Distributed
 Australia,
Kangaroos, but No
Rabbits
 S. America, Llamas
copyright cmassengale
3


ALREADY in NOTES…Just going over!
4 Basic Principles:
1. Individuals in a population show difference, or
variation
 2. Variations can be inherited-meaning passed down
from parent to offspring.
 3. Organisms have more offspring than can survive
on available resources.
 4. Variations that increase reproductive success will
have a greater chance of being passed on than those
that do not increase reproductive success.

• Individuals who
inherit
characteristics most
fit for their
environment are
likely to leave more
offspring than less
fit individuals
• Called Natural
Selection
copyright cmassengale
5
Darwin’s
Theory of
Evolution
•The unequal ability of individuals to
survive and reproduce leads to a gradual
change in a population, with favorable
characteristics accumulating over
generations (natural selection)
•New species evolve
copyright cmassengale
6



1. The Struggle for Existence (compete for
food, mates, space, water, etc.)
2. Survival of the Fittest (strongest able to
survive and reproduce)
3. Descent with Modification (new species
arise from common ancestor replacing less
fit species)
copyright cmassengale
7

Fitness


Ability of an Individual To Survive &
Reproduce
Adaptation


Inherited Characteristic That
Increases an Organisms Chance for
Survival
Can you name some examples of
adaptations for organisms?
copyright cmassengale
8
• Evolution is
the slow ,
gradual
change in a
population
of organisms
over time
copyright cmassengale
9
Evidence of Evolution – The Fossil Record
copyright cmassengale
10
Similarities in DNA Sequence
copyright cmassengale
11
Evolution
of pesticide
resistance
in response
to selection
copyright cmassengale
12
Evidence for Evolution – Evolution Observed
Evolution of drug-resistance in HIV
copyright cmassengale
13



The study of the distribution of plants and
animals around the world.
Patterns of distribution of living and fossil
species tell us how modern organisms evolve
from their ancestors.
Two patterns: Closely related but different and
distantly related but similar

Homologous structures-similar structures in
species sharing a common ancestor
The forelimbs of all mammals consist of the same skeletal
parts. The hypothesis that all mammals descended from a
common ancestor predicts that their forelimbs would be
variations of the structural form in that ancestor.


Structures that are the reduced forms of
functional structures in other organisms.
Evolutionary theory predicts that features of
ancestors that no longer have a function for
that species will become smaller over time until
they are lost.

Examples:
 Snake Pelvis
 Kiwi Wings
 Human Appendix

Can be used for the same purpose and can be
superficially similar in construction but are not
inherited from a common ancestor.

Examples:
 Bald Eagle and the Fly
 What is their similarity?


Similar patterns of embryological development
provide evidence that organisms descended
from a common ancestor.
The same group of cells develop in the same
order and produce homologous tissues in
vertebrates.
Evidence for Evolution - Comparative Embryology
Similarities In Embryonic Development
copyright cmassengale
22



At the molecular level, the universal genetic
code and homologous molecules provide
evidence of common descent.
Genetic code is universal for all organisms.
Homologous molecules are found in various
organisms and have similar functions.
Evolutionary
Time Scales
Macroevolution:
Long time scale
events that create
and destroy
species.
copyright cmassengale
26
Evolutionary
Time Scales
Microevolution:
Short time scale
events (generationto-generation) that
change the
genotypes and
phenotypes of
populations
copyright cmassengale
27

Any change in the allelic frequencies in a
population that results from CHANCE

Founder Effect
 Grand Canyon

Bottleneck Effect
 Disease, Natural
Disaster
If individuals in the group tend to marry within it,
there's a greater likelihood that the recessive genes
of the founders will come together in the cells that
produce offspring. Thus diseases of recessive
genes, which require two copies of the gene to
cause the disease, will show up more frequently
than they would if the population married outside
the group.
https://www.youtube.com/watch?v=_eAJDQ_SgDk

A population in genetic equilibrium
experiences no gene flow
In reality, few populations are isolated.
 Closed system, no new genes entering or leaving
 Random movement of individuals, ex: migration,
which reduces differences between populations





Rarely is mating completely random in a
population.
Usually, organisms mate with individuals in
close proximity.
This promotes inbreeding
Favors homozygous traits

Recall that a mutation is a random change in
genetic material.


Can cause harm or death
However, some mutations provide advantages.