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Table 13.1 Page 218. Table 13.1  Summary of Processes and Patterns of Evolution. Microevolutionary Processes. Mutation . Original source of alleles.

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table 13 1 page 218
Table 13.1Page 218

Table 13.1  Summary of Processes and Patterns of Evolution

Microevolutionary Processes

Mutation

Original source of alleles

Stability or change in a species is the outcome of balances or imbalances among all of these processes, the effects of which are influenced by population size and by the prevailing environmental conditions.

Gene flow

Preserves species cohesion

Genetic drift

Erodes species cohesion

Natural selection

Preserves or erodes species cohesion, depending on environmental pressures

Macroevolutionary Processes

Genetic persistence

Basis of the unity of life. The biochemical and molecular basis of inheritance extends from the origin of first cells through all subsequent lines of descent.

Genetic divergence

Basis of life’s diversity, as brought about by adaptive shifts, branchings, and radiations. Rates and times of change varied within and between lineages.

Genetic disconnect

Extinction. End of the line for a species. Mass extinctions are catastrophic events in which major groups are lost abruptly and simultaneously.

speciation

Speciation

Species- Individuals capable of successful interbreeding and producing fertile offspring.

Speciation: process by which new species come into being

Genetic divergence of reproductively isolated populations

slide3

Simplified diagram of genetic divergence

time A

time B

time C

time D

daughter species

parent species

time

reproductive isolating mechanisms
Reproductive Isolating Mechanisms
  • Prezygotic Isolation
    • Ecological
    • Temporal
    • Behavioral
    • Gametic Mortality
  • Postzygotic Isolation
    • Zygotic Mortality
    • Hybrid Inviability
    • Hybrid Infertility
slide7

Different species!

Temporal isolation

Mechanical isolation

Behavioral isolation

Ecological isolation

They interbreed anyway.

Gamete mortality

Zygotes form, but...

Do not post

to Internet

Hybrid inviability

Hybrid sterility

No offspring or weak offspring that die before reproducing

types of speciation
Types of Speciation
  • Sympatric Speciation- Isolation within a population
    • New species arises in the midst of the original population.
      • Ex: Lake Victoria Cichlids

Allopatric Speciation- Geographical isolation

    • Thought to be most common means of speciation
    • A geographic barrier, such as a river or a mountain range, causes the splitting of a population such that individuals of these now-separate populations can no longer interbreed.
      • Ex: Grey Squirrels around the Grand Canyon
    • Pioneering individuals may colonize a new habitat, such as an oceanic island.
      • Ex: Hawaiian Honeycreeper
slide10

The shared ancestor of all

of Hawaii’s honeycreepers

probably looked like this

house finch (Carprodacus)

Akepa

(Loxops coccineus)

Nihoa finch

(Telespyza ultima)

Palila

(Loxioides bailleui)

Akekee

(L. caeruleirostris)

Maui parrotbill

(Pseudonestor xanthrophrys)

Kauai Amakihi

(Hemignathus kauaiensis)

Akiapolaau

(H. munroi)

Alauahio

(Paroreomyza montana)

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Akohekohe

(Palmeria doli)

Apap

(Himatione sanguinea)

liwi

(Vestiaria coccinea)

slide12

1

A few individuals of a species on the mainland reach isolated island 1. Speciation follows genetic divergence in a new habitat.

3

2

4

Later in time, a few individuals of the new species colonize nearby island 2. In this new habitat, speciation follows genetic divergence.

1

2

Speciation may also follow colonization of islands 3 and 4. And it may follow invasion of island by genetically different descendants

of the ancestral species.

1

3

2

4

patterns of speciation
Patterns of Speciation
  • Phylogeny- The evolutionary relationships among living, or extinct, organisms.
  • Evolutionary Trees- Summarize information about the continuity of relationships among species; summarize phylogenies
    • Branching in the tree represents speciation.
    • Angling of a branch represents gradual change in a lineage= phyletic evolution.
    • A straight line represents no change in a lineage.
    • Branches ending before the present represents extinction.
    • Adaptive radiation- Burst of divergence (branches) from a single lineage.
slide15

species 2

species 3

species 1

suspected branching

a single

lineage;

ancestral

stock

branch point (time of

genetic divergence,

speciation under way)

slide17

Kingdom

Animalia

Animalia

Phylum

Anthropoda

Chordata

Class

Insecta

Mammalia

Order

Diptera

Primates

Family

Muscidae

Hominidae

Genus

Musca

Homo

Species

M. domestica

H. sapiens

Plantae

Plantae

Coniferophyta

Anthophyta

Coniferopsida

Monocotyledonae

Coniferales

Asparagales

Cupressaceae

Orchidaceae

Juniperus

Vanilla

J. occidentalis

V. planifolia

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slide20

Eubacteria

Archaebacteria

Protista

Fungi

Plantae

Animalia

slide21

ANIMALS

PLANTS

arthropods

chordates

FUNGI

conifers

flowering plants

annelids

roundworms

echinoderms

ginkgos

sac

club

mollusks

fungi

fungi

cycads

horsetails

rotifers

zygospore-

ferns

forming

flatworms

fungi

cnidarians

lycophytes

bryophytes

sponges

chlorophytes

chytrids

green algae

amoeboid

PROTISTANS

protozoans

(stramenopiles)

(alveolates)

red

brown algae

ciliates

algae

chrysophytes

sporozoans

oomycotes

?

dinoflagellates

crown of eukaryotes

euglenoids

(rapid divergences)

slime molds

kinetoplastids

parabasalids

(e.g., Trichomonas)

EUBACTERIA

spirochetes

diplomonads

ARCHAEBACTERIA

(e.g., Giardia)

extreme

Gram-positive bacteria

chlamydias

halophiles

methanogens

cyanobacteria

proteobacteria

extreme

thermophiles

molecular origin of life

cladistics
Cladistics
  • Cladistics- Classification based solely on evolutionary relationships.
    • Classification of organisms matches their evolutionary history and expresses the history in branching trees known as cladogram.
    • Clade-The entire portion of a phylogeny that is descended form common ancestor.
how do we construct evolutionary trees using cladistics
How do we construct evolutionary trees using cladistics?
  • Identify ancestral and derived traits.
    • Ancestral traits- Traits shared with a common ancestor
      • Most mammals have four limbs, having inherited this from common ancestor.
    • Derived traits- A trait that differs from the ancestral trait in a lineage.
      • Homologous Traits- Traits derived from a common ancestor.
      • Most mammalian limbs terminate in five digits, but in the hooved animals, there is only one. This trait, having only one digit, is a homologous trait and could be used to group all the hooved animals together.
slide24

1

early reptile

2

3

4

5

1

2

3

pterosaur

4

1

chicken

2

3

1

2

bat

1

3

4

5

porpoise

2

4

5

3

penguin

2

3

1

2

human

3

4

5

difficulties in determining homologous traits
Difficulties in determining homologous traits
  • Not all resemblances are products of common ancestry.
    • Homoplasy- Some traits are the product of convergent evolution, the evolution of the same trait in different lineages
      • Ex: Australian mammals vs. N. American Mammals
species that share a common ancestor should share many homologous traits
Species that share a common ancestor should share many homologous traits
  • Therefore, if two species share the same trait, systematists should, until proven otherwise, assume that the trait is homologous, i.e. none of the traits are the product of convergent evolution.
slide29

shark

mammal

crocodile

bird

fur

feathers

gizzard

lungs

heart

constructing a cladogram
Constructing a Cladogram
  • Assumptions
    • Evolution of traits is irreversible, i.e. an ancestral trait can change into a derived one, but not the reverse.
    • Each trait can change only once in a lineage.
constructing a cladogram1
Constructing a Cladogram
  • Determine an outgroup, a taxon that is closely related to the group whose phylogeny is being constructed, but that branched off from the lineage of the group below its base on the evolutionary tree.
    • You know it’s different from the rest. It’s the one that’s “not like the others”.
  • Select traits that are believed to be homologous.
      • For each taxon, determine whether it has, or is lacking, that trait.
        • (+) indicates the presence of the trait in that taxon.
        • ( - )indicates the lack of the trait in that taxon.
  • Taxa with more homologous traits, have a more recent common ancestor, i.e. they are farther up the tree
slide34

elephants, proboscideans

kangaroos, marsupials

platypus, monotremes

shrews, other

Insectivores, bats

horses, other

perissodactyls

whales, dolphins

deer, other

artiodactyls

carnivores

armadillos

manatees

anteaters

primates

rodents

rabbits

CENOZOIC

MEZOZOIC

ancestral mammal