Name: Date:Biology 11E: Evolution, The Origin of Species

(Chapter 24)

Big Ideas:Big Idea Chapters Illustrative Examples

1. The process of evolution drives the diversity and unity of life.1.a.1 Natural selection is a major mechanism of evolution

22.2, 23.2 • Graphical analysis of allele frequencies in a population• Application of the Hardy-Weinberg equilibrium equation

1.a.2 Natural selection acts on phenotypic variations in populations

23.1, 23.4 • Flowering time in relation to global climate change• Peppered moth• Sickle-Cell Anemia• DDT resistance in insects• Artificial selection• Loss of genetic diversity within a crop species• Overuse of antibiotics

1.a.3 Evolutionary change is also driven by random processes

23.3

1.a.4: Biological evolution is supported by scientific evidence from many disciplines, including mathematics

22.3, 25.2 • Graphical analysis of allele frequencies in a population• Analysis of sequence data sets• Analysis of phylogenetic trees• Construction of pylogenetic trees based on sequence data

1.b.1: Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today.

25.1, 25.3 • Cytoskeleton (a network of structural proteins that facilitate cell movement, morphological integrity and organelle transport)• Membrane-bound organelles (mitochondria and/or chloroplasts)• Linear chromosomes•Endomembrane systems, including the nuclear envelope

1.b.2: Phylogenetic trees and cladograms are graphical representations (models) of evolutionary histories can be tested.

26.1, 26.2, 26.3 • Number of heart chambers in animals• Opposable thumbs• Absence of legs in some sea mammals

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Big Idea Big Idea Big Idea1. The process of evolution drives the diversity and unity of life.1.c.1: Speciation and extinction have occurred throughout the Earth’s history,

24.3, 24.4, 25.4 • Five major extinctions• Human impact on ecosystems and species extinction rates

1.c.2: Speciation may occur when two populations become reproductively isolated from each other.

24.1

1.c.3: Populations of organisms continue to evolve.

24.2 • Chemical resistance• Emergent diseases• Observed directional phenotypic change in a population• A eukaryotic example that describes evolution of a structure or process such as heart chambers, limbs, the brain and the immune system.

1.d.1: There are several hypotheses about the natural origin of life on Earth, each with supporting scientific evidence

4.1, 25.1, 25.3

1.d.2 Scientific evidence from many different disciplines supports models of the origin of life.

26.6

Evolution: The Origin of Species

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Text Chapter: 24Purpose: To explore and understand the mechanisms involved in species evolution and how it has created the diversity of life we see around ourselves today.

The Biological Species ConceptBoth of the birds to the right are Cormorants inhabiting the southern hemisphere. Are they the same species? ____________________________________________________

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Do you think the DNA of the Flightless Cormorant is very similar to that of the Neotropic Cormorant? What could this suggest?____________________________________________________

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Does the evolution of the Flightless Cormorant from the mainland species represent a microevolution or microevolution event?______________________________________________________________________________

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The breakdown of which of the following evolutionary mechanisms allowed for the evolution of the new Flightless Cormorant species?

Mutation Genetic Drift Gene Flow Sexual Selection Natural Selection*Absence of the exchange of alleles (reproductive isolation) plays a key role in macroevolution! This is a result of two different types of reproductive barriers:

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Flightless Cormorant, Galapagos Islands

Neotropic Cormorant, South America

a) Pre-zygotic Barriers: Barriers to gene flow that prevent the creation of a zygote.

b) Post-zygotic Barriers: Barriers to gene flow after the zygote has formed.

*Complete Origin of Species Exercise 3.

Geographic Barriers and SpeciationGene flow can be interrupted in two main ways and lead to speciation:

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By which of the types of speciation above did the Flightless Cormorant evolve? _____________

How do the newly separated populations become different from one another over generations?______________________________________________________________________________

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a) Allopatric Speciation

Requires a _____________ ______________________ to create a new species over thousands of years.What does the graph below reveal about the relationship between reproductive isolation and distance between populations of dusky salamanders?______________________________________________________________________________

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To the right is an experiment in which fruit fly populations were experimentally separated and raised under different conditions (media). What does the experiment demonstrate?______________________________________

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______________________________________*Try Origin of Species Exercises 4 and 6.b) Sympatric SpeciationSpeciation occurs without a geographic barrier. Gene flow is reduced by:

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i) Sexual SelectionSexual selection by female based on physical appearance (colour of male dorsal fin) is believed to have created around 600 different species of Cichlids in Lake Victoria!

Females will mate with their own species under normal light conditions, but can’t differentiate in orange light and will mate with either species. This results in viable, fertile hybrids (so recent speciation).

ii) Habitat DifferentiationA subpopulation exploiting a resource not used by the parent population can result in a barrier to gene flow forming (e.g. temporal isolation if the resource is available in a different season).

iii) PolyloidyPolyploidy is when an organism possesses extra sets of chromosomes. This condition is created through mistakes in cell division and is more common in plants than animals.

There are two types of polyploidy:

1. Autopolyploid: _______________________________________________________________

Tetraploids mating with each other can produce viable/fertile offspring, but mating between 4n and 2n plants produces a 3n plant with reduced hybrid viability = reproductive isolation.

2. Allopolyploid: _______________________________________________________________

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Most hybrids are sterile because the chromosomes of different species can’t pair at meiosis. However, hybrids can reproduce asexually and in the future mechanisms can make the hybrid fertile.

Important polyploidy plants are: oak trees, tobacco, wheat, cotton and potatoes.

Below are diagrams illustrating how bread wheat evolved from three ancestral species:

*Try Investigation: How Do New Species Arise Through Genetic Isolation?*Try Origin of Species Exercise 5.Hybrid Zones and Reproductive Barriers

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What does the existance of a hybrid zone indicate about the reproductive barriers between the toad species above?______________________________________________________________________________

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There are several possible outcomes in the hybrid zone:

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Several closely related species of the European Flycatcher illustrate the reinforcement of reproductive barriers:

Sympatric males of different species look very different from one another.

Allopatric males of different species look very similar to each other.

In which population is reinforcement occurring?____________________

In which population is fusion potentially occurring?____________________

The breakdown of reproductive barriers resulting in the fusion of populations in demonstrated by Cichlids in Lake Victoria where turbid water conditions have resulted in females being unable to mate according to secondary sexual characteristics.

*Try Origin of Species Exercise 7

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The Rate of SpeciationWe have already discussed two potential models:

Refer to text pages 502-503 for a discussion of speciation rates in sunflowers (supports the punctuated equilibrium model).

Sometimes a single mutation can result in a new species:

What type of reproductive barrier is illustrated?___________________________________________________

Similarly, the change in one allele for flower colour can break down reproductive barriers between closely related species of monkey flowers.

In this case, flower colour was a reproductive barrier due to pollinator preferences. Red was preferred by Hummingbirds and bumblebees preferred pink.

*Try Origin of Species:-Test Your Knowledge Multiple Choice: 1-13-Test Your Knowledge Essay: 1-7-Apply the Concepts: Multiple Choice: 1-12-Apply the Concepts Essay: 1-6

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