Evolution concepts and mechanisms

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Evolution: Concepts
o ut o Co cepts
and Mechanism
AP Biology Rapid Learning Series
Wayne Huang, PhD
Andrew Graham, PhD
Elizabeth James, PhD
Casandra Rauser, PhD
Jessica Habashi, PhD
Sara Olson, PhD
Jessica Barnes, PhD

www.RapidLearningCenter.com/
© Rapid Learning Inc. All rights reserved.

© Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com

1


Learning Objectives
By completing this tutorial, you will learn about:
Understand the concept of
Evolution.
Apply the concept to your
life and the environment
around you.
Hone your skills of analysis
by judging the soundness of
Darwin’s theory of
Evolution.

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Evolution Concept Map
DNA

Chemical
Structure

Genes
Mendelian
Laws
Chromosomes
Meiosis

Structure

Independent
Assortment

Law of
Seg egat o
Segregation

Function
Mitosis

4/37


2


Descent with
Modification
Define “Descent With Modification”
Natural Selection
Inheritance

Descent with Modification
Evolution is the change in
inherited traits of a
population.

Changes in genes are a
function of mutations and
selection.

Selection acts on the
“generations”. Bacteria
with a life span of 20 – 45
minutes will evolve more
rapidly then an organism
that requires years to
produce new
generations.

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3


Natural Selection
To understand Darwin’s
theory you need to
understand the meaning
of : descent,
descent
modification and natural
selection.

Modification
M difi ti
Modification is a
mechanism or process of
interaction between the
environment and an
organisms heritable
constitution
adaptation

Descent
Refers to the idea that
current day organisms arose
from older ancestral species
over time.

Natural Selection
The process in which
favorable traits that are
heritable become more
common in subsequent
generations.

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Definition of Inheritance
Heritable and inheritance
describes a trait that can be
passed down from one generation
to the next. This includes hair
color, height etc.
l h i ht t

8/37


4


Modification = Natural Selection
The main mechanism of modification is via “Natural Selection”.

Random
variation of
traits in a
population
Adaptation
more offspring
y g
carrying
advantageous
traits

9/37

Interaction of
species with
environment
Differential
reproductive
success of
species
carrying
particular traits

Natural Selection Targets
Natural selection acts on the
phenotype which is the
observable characteristics of
an organism.

Individuals with favorable
phenotypes are more likely
to survive and reproduce
than those with less
favorable phenotypes.
f
bl h
t

Over time this will result in an
“adaptation” which causes
the organism to specialize for
a certain niche. This can
even lead to the emergence of
a new species.

10/37

If the phenotype is due to a
genetic difference that
genotype will be selected for
and its frequency in the next
generation increased.


5


Genetic Variation and Selection
Genetic variation can occur when
different organisms of a population
have different versions of a gene
(allele).
(allele)
Beak variation is
an example.

Some traits are the result of a single gene.
Most traits are a result of interactions of many
genes. Pleiotropy happens when a single gene
influences many different phenotypic traits. A
new mutation in the gene will have effects on
all traits simultaneously. Genetic linkage
occurs when particular alleles are inherited
together.
11/37

Origin of the
Species
Evolution and speciation
Species origin
Phylogenetic tree


6


Speciation & Origin
A species is a taxonomic
group who's members can
interbreed and produce
fertile offspring.

Speciation is the evolutionary
process giving rise to a new
species. There are four modes of
natural selection that give rise to a
new species and involves
geographic isolation: allopatric,
peripatric, parapatric and sympatric.
New species may also be produced
by genetic engineering and animal
husbandry.

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Kinds of Geographic Speciation
Allopatric speciation, a
population is split into two
geographically isolated
ones. The isolated
populations then undergo
l ti
th
d
genotypic divergence.

Peripatric speciation a new
species is formed in small
isolated peripheral
populations which are
prevented from exchanging
genes with the main
population.
14/37

Parapatric speciation, the
geographic zones of the two
diverging populations are
separate but do overlap.
Individual of each species
may come in contact or
mate but the fitness of the
heterozygote is reduced so
selected against.

Sympatric speciation species
diverge while inhabiting the
same place e.g. insects which
become dependent on
different host plants in the
same area.


7


Phylogenetic Tree of Life
A phylogenetic tree is a branching graph that
shows the evolutionary interrelationships
between species and shows the common
ancestor. Each node represents the most
recent common ancestor of the
descendants. The lengths of the branches
are time estimates.

15/37

Phylogenetic Tree
Speciation events are shown
in this phylogenetic tree. The
relationship between
ancestor and descendant is
based on the number of
shared characteristics
h
d h
i i
between them.

Old world
monkeys
k

New World
Monkeys

Pro-simians

Gorillas

Gibbons
Orangutans Gibb

Chimpanzees
Humans
16/37


8


Darwin’s Theory
Reproduction
Genetic variation
Darwin’s Hypothesis

Reproduction Effects on Evolution

Sir Darwin, can you
y
tell me about your
observations that
lead you to the
theory of evolution?

First I observed that reproducing
organisms will produce more
offspring then the environment can
pp
p g
support if all offspring survive to
reproduce. This is the struggle for
existence.

18/37


9


Darwin & Genetic Variation

Sir Darwin how does
genetics impact your
theory?

I observed that for any given
population of individuals there is a
range of heritable characteristics.

19/37

Survival & Inherited Traits
How does an
organism’s traits
effect a species?

20/37

Survival depends on an
organisms inherited traits. If
a trait or set of traits enables
an organism to survive and
g
reproduce that species will
survive.

See these birds? Ability to
fly high and hunt will be
helped by big wings in some
environments. In other
environments like dense
forests smaller wings will
have the advantage.


10


Darwin’s Hypothesis
The hypothesis states that the
attributes leading to a better fit in
an environment leads to a greater
chance of survival and leaving
behind viable offspring.

Disproportionate reproductive
success within population
members gradually leads to a
change in traits of that particular
population.

21/37

Support for Darwin’s Hypothesis

How can you test
your theory?

The theory is tested by looking
into the fossil record and
studying taxonomy. By
comparing embryological and
anatomical information
similarities and ancestry can be
discovered.

Today with modern
molecular biology
techniques, it is possible
to determine evolution on
the basis of genetics.

22/37


11


Fossils and Evolution Support
Fossils are ancient
impressions left by
biological forms in
sedimentary rock
rock.
These impressions
often reveal the skeletal
framework of an extinct
species.

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Fossil Records
Younger fossils have
species with traits
common to older
fossils plus some
additional traits or
similar traits
reorganized.

The oldest fossils
record the oldest
species living.

Jurassic "clams"

Cretaceous
ammonite

Cretaceous
ichthyosaur

Miocene beaver skull

24/37

Pleistocene saber
toothed cat

Fossil record
indicates that there
are shared traits
between ancestors
and descendants.
This supports
Darwin’s theory.

Pleistocene mammoth


12


Taxonomy Science of Classification
Taxonomy is the science of
classification. It is a
hierarchical grouping of
organisms with descending
i
ith d
di
categories having more
specific characteristics.
Organization is based on
similarity of traits.

25/37

Taxonomic Groupings
The taxonomic grouping
support Darwin’s theory
that all species within a
group can be shown to be
related to one another.

Taxonomic groupings are
by shared traits among
different species leading to
evolutionary relatedness.

Flowers having similar traits
would be grouped together.

26/37


13


Comparative Taxonomy
Comparative Anatomy, Embryology:
These lines of evidence involve making
comparisons of various structures and
i
f
i
t
t
d
determining the degree of similarity among them.
For Example, flippers, wings, paws, hands.
All have similar bone structures, despite overall
external differences - Remember descent with
modification

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Genetics & Darwin’s Theory
Mechanisms of genetic
evolution include: natural
,
,
selection, mutation, random
genetic drift and gene flow.

Genetic evolution refers to
the change in the frequency
of a gene or alleles in a
population.

Natural selection is the best
explanation for genetic
evolution.
evolution Once gene
frequencies change and
adaptation due to natural
selection occurs, advantageous
genes will be selected again and
again because of directional
selection.
28/37


14


Evidence Summary
Types of
Evidence

Does the evidence
corroborate Darwin’s Theory
Darwin s

Fossil
Record

Yes

Taxonomic
Groups

Yes

Independent
Traits

Yes
Y

Genetics

Yes

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Modern
Evolutionary
Theory
Variations of evolutionary theory.
Environmental effects and selection.


15


Variations on Evolutionary Theory
My original theory
believed that evolution
was a very gradual
p
process. Referred to
as gradualism.

Today evidence shows
that evolution may be
better characterized by
punctuated equilibrium. A
spurt and plateau pattern.

Darwin

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Environment and Evolution
The ecosystem plays a
bigger role in stimulating
accumulation of new
species then was previously
thought.

Yes, an example is dinosaur
extinction which is thought
to be a consequence of
climate change.

Environmental changes can
select for new traits required
by that environment and lead
to new species formation.

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16


Gene Flow & In Breeding
There are other mechanisms of
species modification that have a
minor role in evolution of species.
These include: gene flow and non
nonrandom mating (in breeding).

Gene flow: individual
species breed outside their
native group.
ti
Non random mating: in
breeding mating is not
random.

33/37

Question: Review
The process in which favorable
traits become more frequent.

Natural selection
___________

The science of classification.

Taxonomy
___________

What record supports
Darwin’s hypothesis?

Fossil record
___________

Evolution is characterized by
spurts and plateaus, this is
t
d l t
thi i
known as what?

Punctuated equilibrium
___________

Minor mechanisms of
evolution include these.

Gene flow, in-breeding

___________

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17


Learning Summary
Darwin’s theory
may be
described as
“descent with
modification”.

The major force
in evolution is
natural selection

Survival of the fittest
means an organism
can create offspring
that are viable.

Genetic variation
can occur when
different
organisms of a
population have
different versions
of a gene (allele).

The fossil record and
molecular biology
support Darwin’s
theory.

Congratulations
You have successfully completed
the core tutorial

Evolution


18


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What’s N t
Wh t’ Next …

Step 1: Concepts – Core Tutorial (Just Completed)
Step 2: Practice – Interactive Problem Drill
Step 3: Recap – Super Review Cheat Sheet

Go for it!

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Evolution concepts and mechanisms

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