Chapter 24: The Origin of Species. Question? What is a species? Comment - Evolution theory must...

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Chapter 24: The Origin of Species

Transcript of Chapter 24: The Origin of Species. Question? What is a species? Comment - Evolution theory must...

Page 1: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Chapter 24:The Origin of Species

Page 2: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Question? What is a species? Comment - Evolution theory must also

explain how species originate.

Page 3: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Question How many species of African Violets are

here?

Page 4: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Two Concepts of Species1. Morphospecies

2. Biological Species

Page 5: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Morphospecies Organisms with very similar morphology or

physical form.

Page 6: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Problem Where does extensive phenotype variation

fit?

Page 7: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Two Schools1. Splitters - Break apart species into new ones

on the basis of small phenotype changes.2. Lumpers - Group many phenotype variants

into one species.

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Biological Species A group of organisms that could interbreed in

nature and produce fertile offspring.

Page 9: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Key Points Could interbreed. Fertile offspring.

Page 10: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Morphospecies & Biological Species

Often overlap. Serve different purposes.

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African Violets 15+ species 5+ varieties (natural hybrids) 50,000 cultivars

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Example Problem S. magungensis Cluster:

S. Magungensis S. magungensis var. minima S. magungensis var. occidentalis

Page 13: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Current Placement One species and two varieties. However :

Not all live in the same habitat. Not all flower under the same temperatures.

Page 14: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Possible New Placement

Two species and one variety. S. magungensis var. occidentalis may be a new

species.

Page 15: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Speciation Requires:1. Variation in the population.

2. Selection.

3. Isolation.

Page 16: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Reproductive Barriers Serve to isolate a populations from other gene

pools. Create and maintain “species”.

Page 17: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Main Types of BarriersPrezygotic - Prevent mating or fertilization.

Postzygotic - Prevent viable, fertile offspring.

Page 18: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Prezygotic - Types1. Habitat Isolation

2. Behavioral Isolation

3. Temporal Isolation

4. Mechanical Isolation

5. Gametic Isolation

Page 19: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Habitat Isolation Populations live in different habitats or

ecological niches. Ex – mountains vs lowlands.

Page 20: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Behavioral Isolation Mating or courtship behaviors

different. Different sexual attractions

operating. Ex – songs and dances in birds.

Page 21: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Temporal Isolation Breeding seasons or time

of day different. Ex – flowers open in

morning or evening.

Page 22: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Mechanical Isolation Structural differences that prevent gamete

transfer. Ex – anthers not positioned to put pollen

on a bee, but will put pollen on a bird.

Page 23: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Gametic Isolation Gametes fail to attract each other and fuse. Ex – chemical markers on egg and sperm fail

to match.

Page 24: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Postzygotic Types1. Reduced Hybrid Viability

2. Reduced Hybrid Fertility

3. Hybrid Breakdown

Page 25: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Reduced Hybrid Viability Zygote fails to develop or mature. Ex – when different species of frogs

hybridize.

Page 26: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Reduced Hybrid Fertility Hybrids are viable, but can't reproduce

sexually. Chromosome count often “odd” so meiosis

won’t work. Ex - mules

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Hybrid Breakdown Offspring are fertile, but can't compete

successfully with the “pure breeds”. Ex – many plant hybrids

Page 28: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Introgression Transfer of alleles between two species, but

only a partial gene flow. Result – Some intermixing of genes between

two species.

Page 29: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Importance A possible mechanism for gene flow between

similar species.

Page 30: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Question Actively evolving species like Quercus. Good isolation mechanisms or poor ones? Isolation mechanisms may not have fully

developed yet.

Page 31: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Other Concepts of Species

1. Recognition Species Concept

2. Cohesion Species Concept

3. Ecological Species Concept

4. Evolutionary Species Concept

Page 32: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Recognition Species Concept Species are defined by the ability of the

individuals in the population to recognize certain characteristics in each other.

Ex – mate recognition

Page 33: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Cohesion Species Concept

Emphasizes cohesion of phenotypes (complex of genes and set of adaptations).

Page 34: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Ecological Species Concept Emphasizes a species role or function in the

environment.

Page 35: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Evolutionary Species Concept Emphasizes evolutionary lineages and

ecological roles.

Page 36: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Comment AP exam will focus on morphological and

biological species concepts.

Page 37: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Modes of Speciation1. Allopatric Speciation

2. Sympatric Speciation

Both work through a block of gene flow between two populations.

Page 38: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.
Page 39: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Allopatric Speciation Allopatric = other homeland Ancestral population split by a geographical

feature. Comment – the size of the geographical

feature may be very large or small.

Page 40: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Example Pupfish populations in Death Valley. Generally happens when a specie’s range

shrinks for some reason.

Page 41: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Another Example

Page 42: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Conditions Favoring Allopatric Speciation

1. Founder's Effect - with the peripheral isolate.

2. Genetic Drift – gives the isolate population variation as compared to the original population.

Page 43: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Conditions Favoring Allopatric Speciation

3. Selection pressure on the isolate differs from the parent population.

Page 44: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Result Gene pool of isolate changes from the parent

population. New Species can form.

Page 45: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Comment Populations separated by geographical

barriers may not evolve much. Ex - Pacific and Atlantic Ocean populations

separated by the Panama Isthmus.

Page 46: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Examples Fish - 72 identical kinds. Crabs - 25 identical kinds. Echinoderms - 25 identical kinds.

Page 47: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Adaptive Radiation Rapid emergence of several species from a common

ancestor. Common in island and mountain top populations or

other “empty” environments. Ex – Galapagos Finches

Page 48: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Mechanism Resources are temporarily infinite. Most offspring survive. Result - little Natural Selection and the gene

pool can become very diverse.

Page 49: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

When the Environment Saturates Natural Selection resumes. New species form rapidly if isolation

mechanisms work.

Page 50: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Sympatric Speciation Sympatric = same homeland New species arise within the range of parent

populations. Can occur In a single generation.

Page 51: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.
Page 52: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Plants Polyploids may cause new species because

the change in chromosome number creates postzygotic barriers.

Page 53: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Polyploid Types

1. Autopolyploid - when a species doubles its chromosome number from 2N to 4N.

2. Allopolyploid - formed as a polyploid hybrid between two species. Ex: wheat

Page 54: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Autopolyploid

Page 55: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Allopolyploid

Page 56: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Animals Don't form polyploids and will use other

mechanisms.

Page 57: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Gradualism Evolution Darwinian style evolution. Small gradual changes over long periods time.

Page 58: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Gradualism Predicts: Long periods of time are needed for

evolution. Fossils should show continuous links.

Page 59: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Problem Gradualism doesn’t fit the fossil record very

well. (too many “gaps”).

Page 60: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Punctuated Evolution New theory on the “pacing” of evolution. Elridge and Gould – 1972.

Page 61: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Punctuated Equilibrium Evolution has two speeds of change:

Gradualism or slow change Rapid bursts of speciation

Page 62: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Predictions Speciation can occur over a very short period

of time (1 to 1000 generations). Fossil record will have gaps or missing links.

Page 63: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.
Page 64: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Predictions New species will appear in the fossil record

without connecting links or intermediate forms.

Established species will show gradual changes over long periods of time.

Page 65: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Possible Mechanism Adaptive Radiation, especially after mass

extinction events allow new species to originate.

Saturated environments favor gradual changes in the current species.

Page 66: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Comment Punctuated Equilibrium is the newest

”Evolution Theory”. Best explanation of fossil record evidence to

date.

Page 67: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Origin of Evolutionary Novelty How do macroevolution changes originate? Several ideas discussed in textbook.

Exaptation Heterochrony Homeosis

Page 68: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Exaptation

When a structure that was adapted for one context is co-opted for another function.

Ex. – feathers and flying

Page 69: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Heterochrony Changes in the timing or rate of development.

Allometric Growth Paedomorphsis

Page 70: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

1. Allometric Growth – changes in the relative rates of growth of various parts of the body.

Ex. – skull growth in primates

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Page 72: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

2. Paedomorphosis – when an adult retains features that are present in the juvenile form.

Ex. – gills in adult salamanders

Page 73: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.
Page 74: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

HomeosisChanges in the basic body design or arrangement

of body parts.

Ex. – Hox gene clusters that gave rise to vertebrates from invertebrates.

Page 75: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.
Page 76: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Evolutionary Trends Evolution is not goal oriented. It does not

produce “perfect” species.

Page 77: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.
Page 78: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Future of Evolution ? Look for new theories and ideas to be

developed, especially from new fossil finds and from molecular (DNA) evidence.

Page 79: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Summary Be able to discuss the main theories of what is

a “species”. Know various reproductive barriers and

examples.

Page 80: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Summary Know allopatric and sympatric speciation. Be able to discuss gradualism and punctuated

equilibrium theories.

Page 81: Chapter 24: The Origin of Species. Question?  What is a species?  Comment - Evolution theory must also explain how species originate.

Summary Recognize various ideas about the origin of

evolutionary novelties.