Chapter 17 Evolution of Populations

Ch 17.1 Genes and Variation

1.  How is Evolution defined in genetic terms?

Genetics Joins the Evolutionary Theory

Genotypes and phenotypes in evolution.

Plants and animals are unique individuals typically receiving half of the their genetic material from each parent.

Alleles, or different forms of a trait, vary from individual to individual.

An organism’s genotype codes for its phenotype or physical traits.  The variation in these physical traits make some organisms more fit for their environment than others.

Does natural selection work directly on an organism’s genotype (alleles) or phenotype (physical and behavioral characteristics)?  Explain.

Because natural selection acts on an entire organism — the organism either survives or dies- NOT a single gene.

Populations and Gene Pools

Evolution, in genetic terms, involves a change in the frequency of alleles in a population over time.

Think of our Carnation “Bean” lab.

The allele frequency stayed the same (12 red to 4 white beans) BUT the phenotypic frequency changed) proportion of red to pink to white flowers.

Review Video

https://www.youtube.com/watch?v=VdwpoTqjx0k

Sources of Genetic Variation

What are the Sources of Genetic Variation?

There are 3 Sources of Genetic Variation

1.  Mutations

Mutation = any change in the genetic material of a cell

Humans are born with roughly 300 mutations

• most are neutral
• one or two are potentially harmful
• a few may be beneficial

2.  Genetic recombination during sexual reproduction

3.  Lateral gene transfer

Review Video:

Chapter 17 part 2

https://www.youtube.com/watch?v=bRwlygTWE6E

Ch 17.2 Evolution as Genetic Change in Populations

How does natural Selection Affect Single-gene and Polygenetic traits?

1.  Single gene traits

Natural selection on a single gene traits can lead to a change in allele frequencies and thus phenotypic frequencies.

2.  Polygenic traits

Natural selection on polygenic traits can affect the relative fitness of phenotypes and therefore produces one of three different types of natural selection;

Video:  https://www.youtube.com/watch?v=AVInHXjCHlQ 7:11

What is Genetic Drift?

Bottle neck Effect

Founder’s effect

What Conditions are Required to Maintain Genetic Equilibrium?

NOTES:  Berkeley Evolution page:  Bottle Necks and Founder Effect

http://evolution.berkeley.edu/evosite/evo101/IIID3Bottlenecks.shtml

VIDEOS:

Ch 17 part 3 Evolution as Genetic Change

https://www.youtube.com/watch?v=wZMLpEErn6o

Ch 17 part 4 3 Types of Natural Selection

https://www.youtube.com/watch?v=AVInHXjCHlQ

Ch 17 part 5 Founder Effect and Founder Effect

https://www.youtube.com/watch?v=2y-u9ToDfwI

Ch 17 part 6 Hardy-Weinberg Principle

https://www.youtube.com/watch?v=4-ZhpuMyWac

Ch 17.3 The Process of Speciation

What Types of Isolation Lead to the Formation of a New Species?

What is a Current Hypothesis about Galapagos Finch Speciation?

Ch 17.4 Molecular Evolution

What are Molecular Clocks?

A molecular clock uses mutation rates in DNA to estimate the time that two species have been evolving independently.

Simple mutations occur all the time causing slight changes in the sequence of DNA.  Some mutations have a positive or negative effect on an organisms phenotype thus influencing natural selection.

Many mutations have no effect on the phenotype and are considered “neutral” mutations.  These mutations tend to accumulate in the DNA at about a specific rate.

The more differences there are in the DNA sequences between two species, the more time has elapsed since the two species shared a common ancestor.

Example:  Which two of the three species probably shared the most recent common ancestor?  Explain.

Where Do New Genes Come From?

One new way in which new genes evolve is through the duplication and then modification of existing genes.

1.  Copying genes

2.  Duplicate genes

3.  Gene families

How may Hox genes be involved in evolutionary change?

Ch 17.4 Molecular Evolution

Objectives:

Review the Cell Cycle

Read pages 279-285

Activities:

Cell Cycle computer lab

Link for page 1 of hand out

http://www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/cells2.html

Link for On-line Onion Root Tips (page 2 of handout)

http://www.biology.arizona.edu/cell_bio/activities/cell_cycle/cell_cycle.html