Mechanisms of Evolution - PowerPoint PPT Presentation

Loading...

PPT – Mechanisms of Evolution PowerPoint presentation | free to view - id: 7cea2c-NmIwO



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Mechanisms of Evolution

Description:

Mechanisms of Evolution I. Natural Selection & Charles Darwin Charles Darwin (1819-1882) an English scientist considered the founder of the evolutionary theory ... – PowerPoint PPT presentation

Number of Views:104
Avg rating:3.0/5.0
Slides: 33
Provided by: LonH150
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Mechanisms of Evolution


1
Mechanisms of Evolution
2
I. Natural Selection Charles Darwin
  • Charles Darwin (1819-1882) an English scientist
    considered the founder of the evolutionary theory
  • Evolution is often referred to as Darwinism

3
  • Darwin studied many forms of life through the
    voyage of the Beagle
  • Galapagos Islands was where Darwin studied a
    majority of the organism

4
  • Darwin's comparison of the animals of South
    America and the Galapagos Islands caused him to
    conclude that adaptation to the environment can
    cause diversification, including origin of new
    species

5
The Galapagos Islands
  • Darwin notes
  • Island species varied from the mainland species,
    and from island-to-island
  • Each island had either long or short necked
    tortoises depending on the island's vegetation

6
The Galapagos Islands
  • Darwin noted
  • Finches Bill shapes are adaptations to different
    means of gathering food.

7
  • Galapagos finch species varied by nesting site,
    beak size, and eating habits

8
The Theory of Evolution Darwinism
  • We have discussed the 4 supporting evidences of
    evolution.
  • Comparative anatomy
  • Molecular Biology
  • Biogeography
  • Embryology

Today we are going to discuss the 4 mechanisms of
HOW Evolution occurs
9
Outine 4 Mechanisms of Evolution
  1. Natural Selection
  2. Mutation
  3. Migration
  4. Genetic Drift

10
1 Natural Selection
  • Natural Selection AKA Survival of the Fittest
  • A gradual, non-random process by which biological
    traits become either more or less common in a
    population

As you can see there is a variation in the
phenotype of these beetles Green or brown
?
?
11
Genetic Variation Genetic differences within a
population.
The genetic variation in this scenario are the
genes that code for the color of the beetle.
12
3 Types of Natural Selection that Act on
Variation
  • 1. Stabilizing natural selection that favors
    average individuals

13
3 Types of Natural Selection that Act on
Variation
  • 2. Directional selection natural selection
    that favors an extreme form of a trait

14
3 Types of Natural Selection that Act on
Variation
  • 3. Disruptive selection individuals w/ either
    extreme form of a trait

15
2 Mutation
  • Mutation change in a gene alteration of a
    nucleotide sequence.

EX A mutation causes two green beetle parents to
have a brown beetle
16
3 Migration
  • Migration Movement of some individuals to
    another population

Gene Flow transfer of alleles from one
population to another population through
immigration of individuals . This disrupts allele
frequency.
17
4 Genetic Drift
  • Genetic Drift some individuals may by chance and
    not because of fitness leave more descendants
    and therefore pass on their genes.

18
The Evolution of Species
  • Species organisms that look alike can
    interbreed to produce fertile offspring
  • Speciation evolution of a new species.

NOTE Organisms within the same species have
reproductive success ( ability to pass genes onto
the next generation in a way that they too can
pass on those genes.)
Mule
He can not have offspring because his parents are
two different species ?
Donkey
Horse


19
So how do new species come about?
20
Physical Barriers Cause Speciation
  • 1. Geographic Isolation a physical barrier
    divides a population

21
  • 2. Reproductive Isolation the inability of
    organisms to mate and breed fertile offspring
  • Genetic material becomes so different
    fertilization can not occur
  • Behavior mating seasons are different

These Bowerbirds have different mating seasons
and rituals. These 2 factors contribute to
Reproductive Isolation
22
Does evolution happen fast or slow?
23
Both!
Speciation Rates - the time it takes for
evolution to occur. 2 Theories 1
Gradualism idea that species originate through
a gradual change of adaptations
24
  • 2. Punctuated Equilibrium things staying the
    same for a period of time then rapidly changing
    due to a catastrophic event.

25
There are TWO types of Evolution
26
  • 1 Divergent Evolution accumulation of
    differences between groups which can lead to the
    formation of new species

27
  • 2 Convergent Evolution organisms not closely
    relate, independently evolve similar traits (to
    adapt to similar environments.)

28
Genetics Determines Evolution
  • Gene Pool All the alleles in a populations
    genes. In other words every form of a trait
  • Allelic Frequency the of any specific allele
    w/in a gene pool

29
  • Genetic Equilibrium allele frequency remains
    the same over generations
  • Populations in genetic equilibrium are not
    evolving
  • Factors that affects genes can affect equilibrium
  • 1. Mutations negative, positive
  • Negative more than likely causes death
  • Positive may be beneficial

30
Trait Variations differences in Organisms
  • Increases or decreases an organisms chance of
    survival
  • Inherited and controlled by alleles
  • Allelic frequencies in a populations gene pool
    will change due to natural selection

31
(No Transcript)
32
  • C. Patterns of Evolution
  • 1. Adaptive Radiation ancestral species
    evolves into an array of species to fit a
    particular environment.
About PowerShow.com