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Figure 4.3 (b). 24 The Origin of species. Species and Speciation. Fundamental unit of classification is the species. Species = a group of populations in which genes are actually, or potentially, exchanged through interbreeding. Problems

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Figure 4 3 b l.jpg
Figure 4.3 (b)

24 The Origin of species


Species and speciation l.jpg
Species and Speciation

  • Fundamental unit of classification is the species.

  • Species = a group of populations in which genes are actually, or potentially, exchanged through interbreeding.

  • Problems

    • Reproductive criterion must be assumed based on phenotype and ecological information.

    • Asexual reproduction

    • Fossil

    • Geographical isolation


Slide3 l.jpg

  • The origin of new species, or speciation

    • Is at the focal point of evolutionary theory, because the appearance of new species is the source of biological diversity

  • Evolutionary theory

    • Must explain how new species originate in addition to how populations evolve


Microevolution macroevolution and evidence of macroevolutionary change l.jpg
Microevolution, Macroevolution, and Evidence of Macroevolutionary change

~ Bacteria gain resistance to antibiotics over time

  • A change in frequency of alleles in populations over time is called Microevolution.

  • Over longer timescales, microevolutionary processes result in large scale changes that result in formation of new species called Macroevolution(species level)

  • Evidence of Macroevolution- patterns of plant and animal distribution, fossils, anatomical structures, and developmental processes


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Reproductive isolation leads to speciation l.jpg
Reproductive isolation leads to Speciation reproductive isolation

  • the formation of new species

  • Requirement

    • Subpopulations are prevented from interbreeding

    • Gene flow does not occur (Reproductive isolation)

  • Reproductive isolation can result in evolution

  • Natural selection and genetic drift can result in evolution


Speciation of darwin s finches l.jpg
Speciation of Darwin’s Finches reproductive isolation

Warbler


Large ground finch l.jpg
Large ground finch reproductive isolation


Slide9 l.jpg

Similarity between different species. reproductive isolation

The eastern and western meadowlark (Sturnella magna, left) (Sturnella neglecta, right)

songs and other behaviors are different enough

to prevent interbreeding

(a)

Diversity within a species. As diverse as we

may be in appearance, all humans belong to

a single biological species (Homo sapiens),

defined by our capacity to interbreed.

(b)

Figure 24.3 A, B


Reproductive isolation l.jpg
Reproductive Isolation reproductive isolation

  • Reproductive isolation

    • Is the existence of biological factors that impede members of two species from producing viable, fertile hybrids

    • Is a combination of various reproductive barriers


Slide11 l.jpg

  • Prezygotic barriers reproductive isolation

    • Impede mating between species or hinder the fertilization of ova if members of different species attempt to mate

  • Postzygotic barriers

    • Often prevent the hybrid zygote from developing into a viable, fertile adult


Slide12 l.jpg

Prezygotic barriers impede mating or hinder fertilization if mating does occur

Behavioral isolation

Habitat isolation

Temporal isolation

Mechanical isolation

Individualsof differentspecies

Matingattempt

HABITAT ISOLATION

MECHANICAL ISOLATION

TEMPORAL ISOLATION

BEHAVIORAL ISOLATION

(g)

(b)

(d)

(e)

(f)

(a)

(c)

Figure 24.4

  • Prezygotic and postzygotic barriers


Slide13 l.jpg

Gametic mating does occurisolation

Hybridbreakdown

Reducehybridfertility

Reducehybridviability

Viablefertileoffspring

Fertilization

GAMETIC ISOLATION

HYBRID BREAKDOWN

REDUCED HYBRID FERTILITY

REDUCED HYBRID VIABILITY

(k)

(j)

(m)

(l)

(i)

(h)


Limitations of the biological species concept l.jpg
Limitations of the Biological Species Concept mating does occur

  • The biological species concept cannot be applied to

    • Asexual organisms

    • Fossils

    • Organisms about which little is known regarding their reproduction


Other definitions of species l.jpg
Other Definitions of Species mating does occur

  • The morphological species concept

    • Characterizes a species in terms of its body shape, size, and other structural features

  • The paleontological species concept

    • Focuses on morphologically discrete species known only from the fossil record

  • The ecological species concept

    • Views a species in terms of its ecological niche

  • The phylogenetic species concept

    • Defines a species as a set of organisms with a unique genetic history


Slide16 l.jpg

(a) mating does occur

(b)

Sympatric speciation. A smallpopulation becomes a new specieswithout geographic separation.

Allopatric speciation. A population forms a new

species while geographically isolated from its parent population.

Figure 24.5 A, B

  • Concept 24.2: Speciation can take place with or without geographic separation

  • Speciation can occur in two ways

    • Allopatric speciation

    • Sympatric speciation


Allopatric other country speciation l.jpg
Allopatric (“Other Country”) Speciation mating does occur

  • In allopatric speciation

    • Gene flow is interrupted or reduced when a population is divided into two or more geographically isolated subpopulations


Slide18 l.jpg

A. harrisi mating does occur

A. leucurus

Figure 24.6

  • Once geographic separation has occurred

    • One or both populations may undergo evolutionary change during the period of separation


Sympatric same country speciation l.jpg
Sympatric (“Same Country”) Speciation mating does occur

  • In sympatric speciation

    • Speciation takes place in geographically overlapping populations


Habitat differentiation and sexual selection l.jpg
Habitat Differentiation and Sexual Selection mating does occur

  • Sympatric speciation

    • Can also result from the appearance of new ecological niches


Slide21 l.jpg

Monochromatic mating does occur

orange light

Researchers from the University of Leiden placed males and females of Pundamilia pundamilia and P. nyererei together in two aquarium tanks, one with natural light and one with a monochromatic orange lamp. Under normal light, the two species are noticeably different in coloration; under monochromatic orangelight, the two species appear identical in color. The researchers then observed the mating choices of the fish in each tank.

Normal light

EXPERIMENT

P. pundamilia

P. nyererei

Under normal light, females of each species mated only with males of their own species. But under orange light, females of each species mated indiscriminately with males of both species. The resulting hybrids were viable and fertile.

RESULTS

The researchers concluded that mate choice by females based on coloration is the main reproductive barrier that normally keeps the gene pools of these two species separate. Since the species can still interbreed when this prezygotic behavioral barrier is breached in the laboratory, the genetic divergence between the species is likely to be small. This suggests that speciation in nature has occurred relatively recently.

CONCLUSION

Figure 24.10

  • In cichlid fish

    • Sympatric speciation has resulted from nonrandom mating due to sexual selection


Allopatric and sympatric speciation a summary l.jpg
Allopatric and Sympatric Speciation: A Summary mating does occur

  • In allopatric speciation

    • A new species forms while geographically isolated from its parent population

  • In sympatric speciation

    • The emergence of a reproductive barrier isolates a subset of a population without geographic separation from the parent species


Adaptive radiation l.jpg

Figure 24.11 mating does occur

Adaptive Radiation

  • Adaptive radiation

    • Is the evolution of diversely adapted species from a common ancestor upon introduction to new environmental opportunities (typical for long-distance dispersal)

Black noddy tern

Australian coast


Slide24 l.jpg

N mating does occur

1.3 million years

Dubautia laxa

MOLOKA'I

KAUA'I

MAUI

5.1

million

years

Argyroxiphium sandwicense

O'AHU

LANAI

3.7

million

years

HAWAI'I

0.4

million

years

Dubautia waialealae

Dubautia scabra

Dubautia linearis

Figure 24.12

  • The Hawaiian archipelago

    • Is one of the world’s great showcases of adaptive radiation


Slide25 l.jpg

Time mating does occur

(b)

(a)

Gradualism model. Species

descended from a common

ancestor gradually diverge

more and more in their

morphology as they acquire

unique adaptations.

Punctuated equilibrium

model. A new species

changes most as it buds

from a parent species and

then changes little for the

rest of its existence.

Figure 24.13

  • The punctuated equilibrium model

    • Contrasts with a model of gradual change throughout a species’ existence


25 phylogeny and systematics l.jpg
25 Phylogeny and Systematics mating does occur


Slide27 l.jpg


Slide28 l.jpg

Figure 25.1


Slide29 l.jpg

  • Biologists also use systematics mating does occur

    • As an analytical approach to understanding the diversity and relationships of organisms, both present-day and extinct


Slide30 l.jpg

  • Currently, systematists use mating does occur

    • Morphological, biochemical, and molecular comparisons to infer evolutionary relationships

Figure 25.2


Slide31 l.jpg


The fossil record l.jpg

1 inferred from fossil, morphological, and molecular evidence Rivers carry sediment to the ocean. Sedimentary rock layers containing fossils form on the ocean floor.

2 Over time, new strata are deposited, containing fossils from each time period.

3 As sea levels change and the seafloor is pushed upward, sedimentary rocks are exposed. Erosion reveals strata and fossils.

Younger stratum with more recent fossils

Older stratum with older fossils

The Fossil Record

  • Sedimentary rocks

    • Are the richest source of fossils

    • Are deposited into layers called strata

Figure 25.3


Slide33 l.jpg

  • The fossil record inferred from fossil, morphological, and molecular evidence

    • Is based on the sequence in which fossils have accumulated in such strata

  • Fossils reveal

    • Ancestral characteristics that may have been lost over time


Slide34 l.jpg

(c) inferred from fossil, morphological, and molecular evidence Leaf fossil, about 40 million years old

(b) Petrified tree in Arizona, about 190 million years old

(a) Dinosaur bones being excavated from sandstone

(d) Casts of ammonites, about 375 million years old

(f) Insects preserved whole in amber

(e) Boy standing in a 150-million-year-old dinosaur track in Colorado

(g) Tusks of a 23,000-year-old mammoth, frozen whole in Siberian ice

Figure 25.4a–g

  • Though sedimentary fossils are the most common

    • Paleontologists study a wide variety of fossils


Morphological and molecular homologies l.jpg
Morphological and Molecular Homologies inferred from fossil, morphological, and molecular evidence

  • In addition to fossil organisms

    • Phylogenetic history can be inferred from certain morphological and molecular similarities among living organisms

  • In general, organisms that share very similar morphologies or similar DNA sequences

    • Are likely to be more closely related than organisms with vastly different structures or sequences


Sorting homology from analogy l.jpg
Sorting Homology from Analogy inferred from fossil, morphological, and molecular evidence

  • A potential misconception in constructing a phylogeny

    • Is similarity due to convergent evolution, called analogy, rather than shared ancestry


Slide37 l.jpg

Marsupial Australian

mole

Eutherian North Am.

mole

Figure 25.5


Slide38 l.jpg

1 pressures and natural selection Ancestral homologous DNA segments are identical as species 1 and species 2 begin to diverge from their common ancestor.

C C A T C A G A G T C C

1

C C A T C A G A G T C C

2

Deletion

2 Deletion and insertion mutations shift what had been matching sequences in the two species.

1

C C A T C A G A G T C C

C C A T C A G A G T C C

2

Insertion

G T A

3 Homologous regions (yellow) do not all align because of these mutations.

C C A T C A A G T C C

1

C C A T G T A C A G A G T C C

2

4 Homologous regions realign after a computer program adds gaps in sequence 1.

C C A T C A A G T C C

1

Figure 25.6

C C A T G T A C A G A G T C C

2

  • Analogous structures or molecular sequences that evolved independently

    • Are also called homoplasies


Slide39 l.jpg


Binomial nomenclature l.jpg
Binomial Nomenclature classification with evolutionary history

  • Binomial nomenclature

    • Is the two-part format of the scientific name of an organism

    • Was developed by Carolus Linnaeus 1707-1778 (Father of Taxonomy or Systematics)


Slide41 l.jpg


Hierarchical classification l.jpg

Panthera classification with evolutionary history

pardus

Species

Panthera

Genus

Felidae

Family

Carnivora

Order

Mammalia

Class

Chordata

Phylum

Animalia

Kingdom

Eukarya

Domain

Hierarchical Classification

  • Linnaeus also introduced a system

    • For grouping species in increasingly broad categories

Figure 25.8


Linking classification and phylogeny l.jpg

Panthera classification with evolutionary historypardus(leopard)

Mephitis mephitis (striped skunk)

Canis familiaris (domestic dog)

Canislupus (wolf)

Lutra lutra (European otter)

Species

Genus

Panthera

Lutra

Canis

Mephitis

Family

Felidae

Mustelidae

Canidae

Carnivora

Order

Linking Classification and Phylogeny

  • Systematists depict evolutionary relationships

    • In branching phylogenetic trees

Figure 25.9


Slide44 l.jpg

Leopard classification with evolutionary history

Domestic cat

Common ancestor

  • Each branch point

    • Represents the divergence of two species


Slide45 l.jpg

  • Concept 25.3: Phylogenetic systematics informs the construction of phylogenetic trees based on shared characteristics

  • A cladogram

    • Is a depiction of patterns of shared characteristics among taxa

  • A clade within a cladogram

    • Is defined as a group of species that includes an ancestral species and all its descendants

  • Cladistics

    • Is the study of resemblances among clades


Cladistics l.jpg
Cladistics construction of phylogenetic trees based on shared characteristics

  • Clades

    • Can be nested within larger clades, but not all groupings or organisms qualify as clades


Slide47 l.jpg

Grouping 1 construction of phylogenetic trees based on shared characteristics

E

J

K

D

H

G

F

C

I

B

A

(a)Monophyletic. In this tree, grouping 1, consisting of the seven species B–H, is a monophyletic group, or clade. A mono-phyletic group is made up of an ancestral species (species B in this case) and all of its descendant species. Only monophyletic groups qualify as legitimate taxa derived from cladistics.

  • A valid clade is monophyletic

    • Signifying that it consists of the ancestor species and all its descendants

Figure 25.10a


Slide48 l.jpg

Grouping 2 construction of phylogenetic trees based on shared characteristics

G

J

K

H

E

D

C

I

F

B

A

(b)Paraphyletic. Grouping 2 does not meet the cladistic criterion: It is paraphyletic, which means that it consists of an ancestor (A in this case) and some, but not all, of that ancestor’s descendants. (Grouping 2 includes the descendants I, J, and K, but excludes B–H, which also descended from A.)

  • A paraphyletic clade

    • Is a grouping that consists of an ancestral species and some, but not all, of the descendants

Figure 25.10b


Slide49 l.jpg

D construction of phylogenetic trees based on shared characteristics

E

J

G

H

K

I

F

C

B

A

(c)Polyphyletic. Grouping 3 also fails the cladistic test. It is polyphyletic, which means that it lacks the common ancestor of (A) the species in the group. Further-more, a valid taxon that includes the extant species G, H, J, and K would necessarily also contain D and E, which are also descended from A.

  • A polyphyletic grouping

    • Includes numerous types of organisms that lack a common ancestor

Grouping 3

Figure 25.10c


Shared primitive and shared derived characteristics l.jpg
Shared Primitive and Shared Derived Characteristics construction of phylogenetic trees based on shared characteristics

  • In cladistic analysis

    • Clades are defined by their evolutionary novelties (new chars)


Outgroups l.jpg
Outgroups construction of phylogenetic trees based on shared characteristics

  • Systematists use a method called outgroup comparison

    • To differentiate between shared derived (unique to a clade but not found in beyond that taxon) and shared primitive (ancestral) characteristics


Slide52 l.jpg

  • As a basis of comparison we need to designate an outgroup construction of phylogenetic trees based on shared characteristics

    • which is a species or group of species that is closely related to the ingroup, the various species we are studying

  • Outgroup comparison

    • Is based on the assumption that homologies present in both the outgroup and ingroup must be primitive characters that predate the divergence of both groups from a common ancestor


Slide53 l.jpg

TAXA construction of phylogenetic trees based on shared characteristics

Lancelet(outgroup)

Salamander

Leopard

Lamprey

Turtle

Tuna

Hair

0

0

0

0

0

1

CHARACTERS

0

0

0

0

1

1

Amniotic (shelled) egg

0

0

0

1

1

1

Four walking legs

0

0

1

1

1

Hinged jaws

1

0

1

1

1

1

1

Vertebral column (backbone)

(a) Character table. A 0 indicates that a character is absent; a 1 indicates that a character is present.

Leopard

Turtle

Hair

Salamander

Amniotic egg

Tuna

Four walking legs

Lamprey

Hinged jaws

Lancelet (outgroup)

(b) Cladogram. Analyzing the distribution of these derived characters can provide insight into vertebrate phylogeny.

Vertebral column

  • The outgroup comparison

    • Enables us to focus on just those characters that were derived at the various branch points in the evolution of a clade

Figure 25.11a, b


The universal tree of life l.jpg
The Universal Tree of Life construction of phylogenetic trees based on shared characteristics

  • The tree of life

    • Is divided into three great clades called domains: Bacteria, Archaea, and Eukarya

  • The early history of these domains is not yet clear

Bacteria

Eukarya

Archaea

4 Symbiosis of chloroplast ancestor with ancestor of green plants

0

1

3 Symbiosis of mitochondrial ancestor with ancestor of eukaryotes

4

3

Billion years ago

2

2 Possible fusion of bacterium and archaean, yielding ancestor of eukaryotic cells

2

3

1 Last common ancestor of all living things

1

Origin of life

4

Figure 25.18


26 the tree of life an introduction to biological diversity l.jpg
26 The Tree of Life construction of phylogenetic trees based on shared characteristicsAn Introduction to Biological Diversity

  • Overview: Changing Life on a Changing Earth

  • Life is a continuum

    • Extending from the earliest organisms to the great variety of species that exist today


Slide56 l.jpg

Figure 26.1


Slide57 l.jpg

Ceno- construction of phylogenetic trees based on shared characteristicszoic

Meso-zoic

Paleozoic

Humans

Land plants

Origin of solar

system and

Earth

Animals

4

1

Proterozoic

Eon

Archaean

Eon

Billions of years ago

2

3

Multicellular

eukaryotes

Prokaryotes

Single-celled

eukaryotes

Figure 26.10

Atmospheric

oxygen

  • The analogy of a clock

    • Can be used to place major events in the Earth’s history in the context of the geological record


Slide58 l.jpg


The first prokaryotes l.jpg
The First Prokaryotes changed young Earth

  • Prokaryotes were Earth’s sole inhabitants

    • From 3.5 to about 2 billion years ago


Electron transport systems l.jpg
Electron Transport Systems changed young Earth

  • Electron transport systems of a variety of types

    • Were essential to early life

    • Have: some aspects that possibly precede life itself


Photosynthesis and the oxygen revolution l.jpg
Photosynthesis and the Oxygen Revolution changed young Earth

  • The earliest types of photosynthesis

    • Did not produce oxygen


Slide62 l.jpg

Figure 26.12


Slide63 l.jpg


Slide64 l.jpg


The first eukaryotes l.jpg
The First Eukaryotes genetic exchanges between prokaryotes

  • The oldest fossils of a simple eukaryotic cell

    • Date back 2.1 billion years


Endosymbiotic origin of mitochondria and plastids l.jpg
Endosymbiotic Origin of Mitochondria and Plastids genetic exchanges between prokaryotes

  • The theory of endosymbiosis

    • Proposes that mitochondria and plastids were formerly small prokaryotes living within larger host cells


Slide67 l.jpg

Cytoplasm genetic exchanges between prokaryotes

DNA

Plasma

membrane

Ancestral

prokaryote

Infolding of

plasma membrane

Nucleus

Endoplasmic

reticulum

Nuclear envelope

Engulfing

of aerobic

heterotrophic

prokaryote

Cell with nucleus

and endomembrane

system

Mitochondrion

Mitochondrion

Engulfing of

photosynthetic

prokaryote in

some cells

Ancestral

heterotrophic

eukaryote

Plastid

Ancestral

Photosynthetic

eukaryote

Figure 26.13

  • The prokaryotic ancestors of mitochondria and plastids

    • Probably gained entry to the host cell as undigested prey or internal parasites


Slide68 l.jpg


Slide69 l.jpg


Slide70 l.jpg


The earliest multicellular eukaryotes l.jpg
The Earliest Multicellular Eukaryotes eukaryotes

  • Molecular clocks

    • Date the common ancestor of multicellular eukaryotes to 1.5 billion years

  • The oldest known fossils of eukaryotes

    • Are of relatively small algae that lived about 1.2 billion years ago


Slide72 l.jpg

Figure 26.15a, b eukaryotes

(a) Two-cell stage

(b) Later stage

150 m

200 m

  • Larger organisms do not appear in the fossil record

    • Until several hundred million years later

  • Chinese paleontologists recently described 570-million-year-old fossils

    • That are probably animal embryos


The colonial connection l.jpg

10 eukaryotesm

The Colonial Connection

  • The first multicellular organisms were colonies

    • Collections of autonomously replicating cells

Figure 26.16


Slide74 l.jpg

  • Some cells in the colonies eukaryotes

    • Became specialized for different functions

  • The first cellular specializations

    • Had already appeared in the prokaryotic world


Colonization of land by plants fungi and animals l.jpg
Colonization of Land by Plants, Fungi, and Animals eukaryotes

  • Plants, fungi, and animals

    • Colonized land about 500 million years ago


Slide76 l.jpg

Plantae eukaryotes

Fungi

Animalia

Eukaryotes

Protista

Prokaryotes

Monera

Figure 26.21

  • Robert Whittaker proposed a system with five kingdoms

    • Monera, Protista, Plantae, Fungi, and Animalia


Reconstructing the tree of life a work in progress l.jpg
Reconstructing the Tree of Life: A Work in Progress eukaryotes

  • A three domain system

    • Has replaced the five kingdom system

    • Includes the domains Archaea, Bacteria, and Eukarya

  • Each domain

    • Has been split by taxonomists into many kingdoms


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