Chapter 5

Chapter 5

Macroevolution: Processes of Vertebrate and Mammalian

Evolution

Chapter Outline

• The Human Place in the Organic World• Principles of Classification• Definition of Species• Vertebrate Evolutionary History: A Brief

Summary• Mammalian Evolution

Chapter Outline• The Emergence of Major Mammalian Groups• Processes of Macroevolution• Issue: Just When We Thought Things Couldn’t

Get Any Worse: Bushmeat and Ebola

Classification

• Classification is used to order organisms into categories to show evolutionary relationships.

• Example - human classification Kingdom: Animalia Subkingdom: Metazoan Phyla: Chordata Subphyla: Vertebrata Class: Mammalia

Classification: Definitions• Metazoa

Multicellular animals.• Chordata

The phylum of the animal kingdom that includes vertebrates.

• Vertebrates Animals with segmented bony spinal

columns; includes fishes, amphibians, reptiles, birds, and mammals.

Principles of Classification

• The field that specializes in establishing the rules of classification is called taxonomy.

• Organisms are classified first on the basis of physical similarities.

• Basic physical similarities must reflect evolutionary descent in order for them to be useful.

Principles of Classification• Homologies

Similarities based on descent from a common ancestor.

• Analogies Similarities based on common function, with

no assumed common evolutionary descent.• Homoplasy

The separate evolutionary development of similar characteristics in different groups of organisms.

Homologies

Two Approaches to Classification

• Evolutionary systematics A traditional approach in which presumed

ancestors and descendants are traced in time by analysis of homologous characters.

• Cladistics Attempts to make rigorous evolutionary

interpretations based solely on analysis of certain types of homologous characters.

Question

• The scientific discipline that delineates the rules of classification is

a) paleontology.

b) stratigraphy.

c) homology.

d) taxonomy.

Answer: d

• The scientific discipline that delineates the rules of classification is taxonomy.

Ancestral and Modified Characters• Ancestral characters

Refers to characters inherited by a group of organisms from a remote ancestor and thus not diagnostic of groups (lineages) that diverged after the character first appeared.

• Derived characters Refers to characters that are modified from

the ancestral condition and thus are diagnostic of particular evolutionary lineages.

Evolutionary “Trees”: Development of Passenger Vehicles

• The first divergence is between cars and trucks (I).

• A later divergence occurs between luxury cars and sports cars (II).

Evolutionary “Trees”: Development of Passenger Vehicles

• SUVs diverge from trucks, but like sports cars, they have a decorative racing stripe.

• This is a homoplasy and does not make SUVs sports cars.

• Classifications based on a characteristic that can appear independently in different groups can lead to an incorrect conclusion.

Evolutionary Relationships of Birds and Dinosaurs

• (a) Traditional view, showing no close relationship. (b) Revised view, showing common ancestry of birds and dinosaurs.

Cladogram

• Shows relationships of birds, dinosaurs, and other terrestrial vertebrates. There’s no time scale, and both living and fossil forms are shown along the same dimension. Ancestor- descendant relationships aren’t indicated.

Approaches to Classification

Evolutionary Systematics

Cladistics

Goal Construction of a phylogenetic tree

Construction of a cladogram

Similarities •Compare specific traits•Construct classifications to show

evolutionary relationships•Focus on homologies

Approaches to Classification

Evolutionary Systematics

Cladistics

Differences Might use any homologous characterAttempts to make ancestor-descendant links Attempts to place fossils in a chronological framework

Use only defined derived charactersNo conclusions regarding ancestor-descendant relationshipsAll members of an evolutionary group are interpreted in one dimension

Definition of Species

• Biological species concept Depiction of species as groups of

individuals capable of interbreeding, but reproductively isolated from other such groups.


• Recognition species concept A depiction of species in which the key

aspect is the ability of individuals to identify members of their own species for purposes of mating.

This type of selective mating is a component of a species concept emphasizing mating and is therefore compatible with the biological species concept.

Definition of Species• Ecological species concept

The concept that a species is a group of organisms exploiting a single niche.

This view emphasizes the role of natural selection in separating species from one another.


• Phylogenetic species concept Splitting many populations into

separate species based on an identifiable parental pattern of ancestry.

Allopatric

• Living in different areas.• This pattern is important in the divergence

of closely related species from each other and from their shared ancestral species because it leads to reproductive isolation.

Speciation

• Process by which a new species evolves from a prior species.

• Speciation is the most basic process in macroevolution.

Speciation Model

Recognition of Fossil Species

• The minimum biological category we would like to define in fossil primate samples is the species. Variations

• Intraspecific - Variation is accounted for by individual, age, and sex differences seen within every biological species

• Interspecific - Variation represents differences between reproductively isolated groups.

Recognition of Fossil Species

• Defining where species boundaries begin and end is often difficult. “Splitters” are researchers who claim

speciation occurred frequently during hominid evolution.

“Lumpers” assume speciation was less common and see much variation as being intraspecific.

Recognition of Fossil Genera

• A genus is a group of species composed of members more closely related to each other than to species from any other genus.

• Species that are members of the same genus share the same broad adaptive zone.

• Members of the same genus should all share derived characters not seen in members of other genera.

Geological Time Scale

ERA PERIODBegan m.y.a. EPOCH

Began m.y.a.

CENOZOIC

Tertiary 1.8Holocene

Pleistocene

0.011.8

Quaternary 65

PlioceneMiocene

OligoceneEocene

Paleocene

523345565


ERA PERIOD (Began m.y.a.)

MESOZOIC Cretaceous 136

Jurassic 190

Triassic 225

PALEOZOIC

PermianCarboniferous

DevonianSilurian

OrdovicianCambrian

280345395430500570


Geological Eras• Paleozoic

The first vertebrates appeared 500 m.m.y.a. • Mesozoic

Reptiles were dominant land vertebrates. Placental mammals appeared 70 m.Y.A.

• Cenozoic Divided into two periods: Tertiary and

Quaternary and 7 epochs: Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene and Holocene.

Continental Drift

• The movement of continents on sliding plates of the earth’s surface.

• As a result, the positions of large landmasses have shifted drastically during the earth’s history.

Continental drift• The positions of the

continents during the Mesozoic (c. 125 m.y.a.).

• Pangea is breaking up into a northern landmass (Laurasia) and a southern landmass (Gondwanaland).

Continental Drift

• (a) Positions of the continents during the Mesozoic. Pangea is breaking up into a northern landmass (Laurasia) and a southern landmass (Gondwanaland). (b) Positions of the continents at the beginning of the Cenozoic.

Ecological Niches

• The positions of species within their physical and biological environments, together making up the ecosystem.

• A species’ ecological niche is defined by such components as diet, terrain, vegetation, type of predators, relationships with other species, and activity patterns, and each niche is unique to a given species.

Epochs• Categories of the geological time scale. • In the Cenozoic, epochs include

Paleocene Eocene Oligocene Miocene Pliocene Pleistocene Holocene

Mammalian Evolution

• The Cenozoic era is known as the Age of Mammals.

• After dinosaurs became extinct, mammals underwent adaptive radiation, resulting in rapid expansion and diversification.

• The neocortex, which controls higher brain functions, comprised the majority of brain volume, resulting in greater ability to learn.

Reptilian and Mammalian teeth

• Mammals are heterodont, they have different kinds of teeth; incisors, canines, premolars, and molars.

Major Events in Early Vertebrate Evolution

Question

• The divergence of reptiles into many different forms describes

a) analogies.

b) sexual selection.

c) adaptive radiation.

d) homologies.

Answer: c

• The divergence of reptiles into many different forms describes adaptive radiation.

Time Unit Conversion Using the Cosmic Calendar1 yr = 15,000,000,000 yrs 1mth = 1,250,000,000 yrs1 day = 41,000,000 yrs

1 hr = 1,740,000 yrs1 min = 29,000 yrs1 sec = 475 yrs

Big Bang January 1

Formation of the earth September 14

Origin of life on earth September 25

Significant oxygen, atmosphere begins to develop

December 1



Precambrian ends; Paleozoic begins; invertebrates flourish

December 17

Paleozoic ends and Mesozoic begins December 25

Cretaceous period: first flowers; dinosaurs become extinct

December 28

Mesozoic ends; Cenozoic begins; adaptive radiation of placental mammals

December 29



December 31

Appearance of early hominoids 12:30 P.M.

First hominids 9:30 P.M.

Extensive cave painting in Europe 11:59 P.M.

Invention of agriculture 11:59:20 P.M.



December 31

Renaissance in Europe: Ming Dynasty in China; emergence of scientific method

11:59:59 P.M.

Widespread development of science and technology; emergence of a global culture; first steps in space exploration

NOW: the first second of the New Year

Heterodont

• Having different kinds of teeth; characteristic of mammals, whose teeth consist of incisors, canines, premolars, and molars.

Endothermic

• Able to maintain internal body temperature by producing energy through metabolic processes within cells; characteristic of mammals, birds, and perhaps some dinosaurs.

Question• An advantage of heterodont dentition is that it

a) allows the animal to defend itself more efficiently.

b) allows for processing a wide variety of foods.

c) opens up new ways of interacting with potential mates.

d) allows the animal to grab prey that it could not catch otherwise.

Answer: b

• An advantage of heterodont dentition is that it allows for processing a wide variety of foods.

Major Mammalian Groups

• Monotremes Primitive, egg laying mammals

• Marsupials Infants complete development in an eternal

pouch • Placental

Longer gestation allows the central nervous system to develop more completely

Adaptive Radiation

• A process that takes place when a life form rapidly takes advantage of the many newly available ecological niches.

• A species, or group of species, will diverge into as many variations as two factors allow:

1. Its adaptive potential.

2. The adaptive opportunities of the available niches.

Gradualism versus Punctuated Equilibrium

• The traditional view of evolution has emphasized that change accumulates gradually in evolving lineages, an idea called phyletic gradualism.

• Punctuated equilibrium is the concept that evolutionary change proceeds through long periods of stasis punctuated by rapid periods of change.

Chapter 5

Documents

evolutionary trees

common ancestor

suvs sports cars

common ancestry of birds

different groups of

luxury cars

common function

group of organisms