Origin ofspecies

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The Origin Of e O g OSpecies

AP Biology Rapid Learning Series

Rapid Learning Centerwww.RapidLearningCenter.com/

© Rapid Learning Inc. All rights reserved.

AP Biology Rapid Learning SeriesWayne Huang, PhD

Andrew Graham, PhDElizabeth James, PhD

Casandra Rauser, PhD Jessica Habashi, PhD

Sara Olson, PhDJessica Barnes, PhD



Learning Objectives

Understand how new species originate

By completing this tutorial, you will learn about:

species originate.

Know what makes a species a species.

Understand how environmental change effects biodiversity.

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Be able to apply these concepts to understand the continual evolution of species today.

Concept MapSympatric speciation

Speciation

Allopatric Speciation

Biological

Gene Pool Isolation via internal barrier

Truly Satisfy Species

Definition

Morpho-Species

pEvent

Origin Of

Species Biodiversity

Biological Species Concept

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Basic Patterns of Evolution

Concept

CladogenesisAnagenesis



Species Concept

Define species

Morphology species concept

Phenotype and genotype interactions

Species Concepts

There are two approaches to

defining a species

One is based on whether or not animals can breed

with one another anddefining a species.

The second approach depends on morphology.

with one another and produce offspring that

are fertile.

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MorphologyMorphology in biology typically refers to the

outward appearance (shape, structure, color, pattern) of

an organism or taxon and the

This is in contrast to physiology which focuses on function. Gross morphology would include: overall shape, an organism or taxon and the

parts that make it up.p ,

color, major markings etc. but not finer details.

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Morphology Species Concept

Morphospecies is an approach in which an organism’s morphology is compared and

contrasted to that of similar organisms, for the purpose of defining a species.

Lynx

Example: animals belonging to the same i i il i f h d

Lynx

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species are similar in : form, shape and appearance. This is the most used method

in the field.

Bobcat



No they look too different

Morpho-species ApplicationAre these two snakes considered the same species ?

No, they look too different.

Even though different colors, they still look more alike then different, therefore same species.

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Important Terms

Genotype – The genetic makeup of an organism alsomakeup of an organism, also known as genome.

Phenotype – the visible or measurable manifestation of an organism’s traits.

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Genotype + Environment Phenotype



Morph-Species Theory WeaknessThe morpho-species concept is

not sufficiently rigorous to eliminate mistakes in defining a species. A judgment based on appearance or phenotype leadsappearance or phenotype leads

to ambiguity.

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Biological Species Concept

In this approach a species is defined by its

This breeding would result in viable, fertile

offspring. This definition

M l D k F l H

ability to interbreed with members of a specific

population but not others.

p gof species is less

ambiguous.

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Male Donkey + Female Horse = Mule (infertile) Most mules when mated with mules are usually unable to produce

offspring. So by this definition mules would not be

a species.



Weakness of Bio-species Concept

The weakness in the “bio-species concept” to define

species is that it is ineffective for organisms gthat procreate asexually. Such as bacteria, plants,

etc.

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Bio-species & Extinct Organisms

The bio-species method of defining a species is ineffective for extinct organismsis ineffective for extinct organisms. This is because it is not possible to determine if the fossils could have mated.

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Evolutionary Relationships & Biodiversity

Anagenesis verse Cladogenesis

Basic Patterns of Evolution

There are two basic patterns of evolution and speciation;

anagenesis and cladogenesis. Genesis means “origin of life”. g

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AnagenesisAnagenesis is the evolution of species involving a change in

gene frequency in an entire population not just a cladogenetic branching event. The entire population is

different from the ancestral population and the ancestral population is considered extinct

Old world monkeys

New World MonkeysProsimians

population is considered extinct.

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Monkeys

Gorillas OrangutansGibbons

Prosimians

Evolutionary change leading to the prosimian line is a transformation

into a new species without branching i.e. anagenesis.

CladogenesisCladogenesis is an evolutionary splitting

event. A clade is a process of adaptive evolution that leads to the development of

a greater variety of sister organisms.

Old world monkeys

New World MonkeysProsimians

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Gorillas OrangutansGibbons

Evolution of New World monkey line is an example of

cladogenesis. Note branching.



Anagenesis

Biodiversity and EvolutionWhich pattern of evolution would lead to greater species diversity (biodiversity) ?

Anagenesis

Cladogenesis

Hint: all of these primates derived from New World Monkeys

Gorilla Orangutan Gibbon

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Speciation Events

Causes of speciation



Speciation Events: IsolationA new species may be created when a

segment of a population becomes isolated.

This might happen because of new barriers g ppsuch as mountains or bodies of water.

The new species may be defined based on either “morphology” or “biology” definitions.

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Definition of Gene Pool

Gene PoolThe complete set of genes of all

members in a population.

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What Isolates a Gene Pool ?

Barriers to interbreeding and or reproduction leads to gene pool isolation.

Barrier

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Internal Barriers to Gene Flow

Gene Pool Isolation

Two causes:

C ti f fl i t i i t th i• Cessation of gene flow: intrinsic to the organism, part of its genetic make up.

• Gene pool isolation: external to the organism.

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Reproductive isolation may be caused by the production of

sterile offspring (e.g.. Mule) or prevention of fertilization (e.g.

errors in cell division).



Internal Barriers to Fertilization

Wrong Place: organisms occupy different

Internal Barriers to fertilization Gene pool Isolation

habitats / niche and do not meet. For example, tree snakes live in an elevated habitat whereas water moccasins stay in or near the water.

Their evolved adaptations / traits allow them to compete within their niche. It also inhibits their meeting.

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Behavioral Barriers

Wrong Behaviors: dissimilar mating behaviors or rituals no mating. i.e., whale songs very distinctive, species specific & required for mating.

Wrong Anatomy: organisms with grossly different body proportions no mating.

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Infertile Progeny Internal Barrier

Progeny not fertile resulting in no further generations.

Donkey + Horse Mule (sterile) no transfer of b k t i i ti ( t l) l tigenes back to originating (parental) populations

(gene pool isolation).

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External Barrier & Gene Pool

Example of External Barrier to reproduction:

For example, geographic isolation. Shifting land masses islands separating from mainland.

Populations once united can be divided with these land shifts.

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Speciation via External BarriersThe time line below depicts a speciation event known as Allopatric Speciation. That is speciation initiated by external barriers.

Time line

No reproduction / fertilization with parental

Environment Change

Modifications via natural selection or extinction (most)

Time line

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Physical Separation

with parental population

ChangeInternal barriers to reproduction develop = new species

No gene flow between populations. Organism subset interacting with new environment

(most)

Summary of Speciation Events

Barriers to Fertilization

(External at 1st)

Gene Pool Isolation + new

environmentNew species

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Extinction or adaptations via

natural selection

Internal barriers may develop as a byproduct of

adaptations



Sympatric Speciation

S t i i ti i t f i ti t

Sympatric speciation is more important for plant speciation than for animals.

Sympatric speciation is a set of speciation events different from allopatric speciation in the following ways:

Internal barriers develop first without initial external barriers.Internal barriers cause instant reproductive and gene pool isolation.

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Interbreeding Internal BarriersInherent trait of organism leads to decrease or halt of

interbreeding between parental & separated subset populations, even if external barrier no longer exists.g

An example of this type of barrier would be flowers that

bloom at different times preventing cross pollination.

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Sympatric Speciation & Cell DivisionIn speciation by reproductive

isolation, errors in cell division during mitosis can occur. This results in doubling the number

This failure in mitosis results in polyploids; most of which go extinct before

of chromosomes and preventing correct pairing in gametes during fertilization.

reproducing.

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Speciation Speciation Species C tSpecies

C t

Learning Summary

EventsEvents ConceptsConcepts

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Patterns of Evolution

Patterns of Evolution

Evolutionary relationships

and Biodiversity

Evolutionary relationships

and Biodiversity



Question: Review

Two approaches to species definition. ___________

Morphology & viable offspring

Th ti k f ___________

___________

Genotype

Phenotype

The genetic makeup of an organism is called its ____.

is the evolution of a

The visible or measurable expression of an organisms traits.

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___________Anagenesis____species involving a change in gene frequency in the entire population.

____ is an evolutionary splitting event. ___________Cladogenesis

Congratulations

You have successfully completed the core tutorial

The Origin of Species

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Origin ofspecies