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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
Figure 4.3 (b)

24 The Origin of species

species and speciation
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
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
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
slide5
Concept 24.1: The biological species concept emphasizes reproductive isolation
  • Species
    • Is a Latin word meaning “kind” or “appearance”
reproductive isolation leads to speciation
Reproductive isolation leads to Speciation
  • 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
slide9

Similarity between different species.

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
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
Prezygotic barriers
    • 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

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

Gameticisolation

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
Limitations of the Biological Species Concept
  • The biological species concept cannot be applied to
    • Asexual organisms
    • Fossils
    • Organisms about which little is known regarding their reproduction
other definitions of species
Other Definitions of Species
  • 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

(a)

(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
Allopatric (“Other Country”) Speciation
  • In allopatric speciation
    • Gene flow is interrupted or reduced when a population is divided into two or more geographically isolated subpopulations
slide18

A. harrisi

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
Sympatric (“Same Country”) Speciation
  • In sympatric speciation
    • Speciation takes place in geographically overlapping populations
habitat differentiation and sexual selection
Habitat Differentiation and Sexual Selection
  • Sympatric speciation
    • Can also result from the appearance of new ecological niches
slide21

Monochromatic

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
Allopatric and Sympatric Speciation: A Summary
  • 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

Figure 24.11

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

N

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

Time

(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
slide27
Overview: Investigating the Tree of Life
  • This chapter describes how biologists trace phylogeny
    • The evolutionary history of a species or group of related species
slide28
Biologists draw on the fossil record
    • Which provides information about ancient organisms

Figure 25.1

slide29
Biologists also use systematics
    • As an analytical approach to understanding the diversity and relationships of organisms, both present-day and extinct
slide30
Currently, systematists use
    • Morphological, biochemical, and molecular comparisons to infer evolutionary relationships

Figure 25.2

slide31
Concept 25.1: Phylogenies are based on common ancestries inferred from fossil, morphological, and molecular evidence
the fossil record

1 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
The fossil record
    • 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

(c) 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
Morphological and Molecular Homologies
  • 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
Sorting Homology from Analogy
  • A potential misconception in constructing a phylogeny
    • Is similarity due to convergent evolution, called analogy, rather than shared ancestry
slide37
Convergent evolution occurs when similar environmental pressures and natural selection
    • Produce similar (analogous) adaptations in organisms from different evolutionary lineages

Marsupial Australian

mole

Eutherian North Am.

mole

Figure 25.5

slide38

1 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
Concept 25.2: Phylogenetic systematics connects classification with evolutionary history
  • Taxonomy
    • Is the ordered division of organisms into categories based on a set of characteristics used to assess similarities and differences
binomial nomenclature
Binomial Nomenclature
  • 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
The binomial name of an organism or scientific epithet
    • Is latinized
    • Is the genus and species
hierarchical classification

Panthera

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

Panthera pardus(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

Leopard

Domestic cat

Common ancestor

  • Each branch point
    • Represents the divergence of two species
slide45
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
Cladistics
  • Clades
    • Can be nested within larger clades, but not all groupings or organisms qualify as clades
slide47

Grouping 1

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

Grouping 2

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

D

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
Shared Primitive and Shared Derived Characteristics
  • In cladistic analysis
    • Clades are defined by their evolutionary novelties (new chars)
outgroups
Outgroups
  • 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
As a basis of comparison we need to designate an outgroup
    • 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

TAXA

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
The Universal Tree of Life
  • 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
26 The Tree of LifeAn 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
Geological events that alter environments
    • Change the course of biological evolution
  • Conversely, life changes the planet that it inhabits

Figure 26.1

slide57

Ceno-zoic

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
Concept 26.3: As prokaryotes evolved, they exploited and changed young Earth
  • The oldest known fossils are stromatolites
    • Rocklike structures composed of many layers of bacteria and sediment
    • Which date back 3.5 billion years ago
the first prokaryotes
The First Prokaryotes
  • Prokaryotes were Earth’s sole inhabitants
    • From 3.5 to about 2 billion years ago
electron transport systems
Electron Transport Systems
  • 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
Photosynthesis and the Oxygen Revolution
  • The earliest types of photosynthesis
    • Did not produce oxygen
slide62
Oxygenic photosynthesis
    • Probably evolved about 3.5 billion years ago in cyanobacteria

Figure 26.12

slide63
When oxygen began to accumulate in the atmosphere about 2.7 billion years ago
    • It posed a challenge for life
    • It provided an opportunity to gain abundant energy from light
    • It provided organisms an opportunity to exploit new ecosystems
slide64
Concept 26.4: Eukaryotic cells arose from symbioses and genetic exchanges between prokaryotes
  • Among the most fundamental questions in biology
    • Is how complex eukaryotic cells evolved from much simpler prokaryotic cells
the first eukaryotes
The First Eukaryotes
  • The oldest fossils of a simple eukaryotic cell
    • Date back 2.1 billion years
endosymbiotic origin of mitochondria and plastids
Endosymbiotic Origin of Mitochondria and Plastids
  • The theory of endosymbiosis
    • Proposes that mitochondria and plastids were formerly small prokaryotes living within larger host cells
slide67

Cytoplasm

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
In the process of becoming more interdependent
    • The host and endosymbionts would have become a single organism
slide69
The evidence supporting an endosymbiotic origin of mitochondria and plastids includes
    • Similarities in inner membrane structures and functions
    • Both have their own circular DNA
slide70
Concept 26.5: Multicellularity evolved several times in eukaryotes
  • After the first eukaryotes evolved
    • A great range of unicellular forms evolved
    • Multicellular forms evolved also
the earliest multicellular eukaryotes
The Earliest Multicellular 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

Figure 26.15a, b

(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

10 m

The Colonial Connection
  • The first multicellular organisms were colonies
    • Collections of autonomously replicating cells

Figure 26.16

slide74
Some cells in the colonies
    • Became specialized for different functions
  • The first cellular specializations
    • Had already appeared in the prokaryotic world
colonization of land by plants fungi and animals
Colonization of Land by Plants, Fungi, and Animals
  • Plants, fungi, and animals
    • Colonized land about 500 million years ago
slide76

Plantae

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
Reconstructing the Tree of Life: A Work in Progress
  • 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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