Chapter 7
Download
1 / 53

Chapter 7 - PowerPoint PPT Presentation


  • 495 Views
  • Uploaded on

Chapter 7 Evolution and the Fossil Record Chapter 7 - Guiding Questions What lines of evidence convinced Charles Darwin that organic evolution produced the species of the modern world? What are the components of natural selection?

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Chapter 7' - Jeffrey


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Chapter 7 l.jpg

Chapter 7

Evolution and the Fossil Record


Chapter 7 guiding questions l.jpg
Chapter 7 - Guiding Questions

  • What lines of evidence convinced Charles Darwin that organic evolution produced the species of the modern world?

  • What are the components of natural selection?

  • What is the source of the variability that is the basis of natural selection?

  • What role does geography play in speciation?

  • What factors lead to evolutionary radiation?

  • Why is convergence one of the most convincing kinds of evidence that evolutionary changes are adaptive?

  • Why do species become extinct?

  • What is mass extinction?

  • In what ways can evolutionary trends develop?


Evolution l.jpg
Evolution

Evolution

  • changes in populations, which consist of groups of individuals that live together and belong to the same species

  • a change in gene frequencies

  • populations evolve, not individuals

    • YOU can’t evolve!

Extinct ground sloth (20 ft long)


Evolution4 l.jpg
Evolution

Adaptations

  • specialized features of animals and plants (or any other organism) which perform one or more useful functions

  • allow that organism to excel in its environment

  • YOU can only modify characteristics over which your genes have control; e.g., tanning

Cat skull

Horse skull

Venus Flytrap


Inefficient evolution l.jpg
Inefficient Evolution

  • can only operate by changing what is already present;

  • it’s the business of remodeling rather than new construction from scratch

  • e.g., to make a new structure, natural selection starts by modifying an already existing one

    • e.g., how could ‘night vision’ evolve?


Charles darwin l.jpg
Charles Darwin

  • 1831

    • set sail on the Beagle

    • schooled in uniformitarianism

      • Lyell’s Principles of Geology

    • a keen observer of natural phenomena

  • 1859-On the Origin of Species by Natural Selection


Some of darwin s observations l.jpg
Some of Darwin’s Observations

  • Rhea

    • large flightless birds

    • found only in South America

    • also found extinct, fossil forms

  • Some similarities but also obvious differences from ostrich (Africa) and emu (Australia)


More of darwin s observations l.jpg
More of Darwin’s Observations

  • sloths and extinct armadillos

    • unique to the Americas


More of darwin s observations9 l.jpg
More of Darwin’s Observations

  • Oceanic islands

    • many barren; Hawaii has no native snakes, frogs, FW fish, etc.

    • species must have originated elsewhere

  • Galápagos Islands

    • tortoises with shells unique on each island

    • shared a common ancestry

    • followed later by differentiation


Galapagos islands l.jpg
Galapagos Islands

Range from 3 to 5 my old


Galapagos tortoises l.jpg
Galapagos Tortoises

  • 14 subspecies, 11 extant, several with very small populations

    • e.g., Lonesome George


Lonesome george l.jpg
Lonesome George

Isla Pinta


Darwin s famous finches l.jpg

  • Finches of the Galápagos

    • different beak types

      • slender-insectivorous

      • sturdy-seed crushing

      • woodpecker-like-tool user

    • differentiation based on lifestyle

    • curiously resemble a South American mainland finch

Darwin’s Famous Finches




Charles darwin16 l.jpg
Charles Darwin

  • Additional observations

    • Anatomical relationships

      • embryos of many vertebrates are quite similar, even superficially indistinguishable


Charles darwin18 l.jpg
Charles Darwin

  • Additional observations

    • Anatomical relationships

      • embryos of many vertebrates quite similar

      • homology

        • presence in two different groups of animals or plants of organs that have the same ancestral origin but serve different functions


Charles darwin20 l.jpg
Charles Darwin

  • Additional observations

    • Anatomical relationships

      • embryos of many vertebrates quite similar

      • homology

        • presence in two different groups of animals or plants of organs that have the same ancestral origin but serve different functions

      • vestigial organs

        • organs that serve no apparent purpose but resemble organs that perform functions in other creatures




Theory of evolution l.jpg
Theory of Evolution

  • Natural Selection- ‘survival of the fittest’

    • the process that operates in nature but parallels the artificial selection by which breeders develop new varieties of plants and animals

      • success of an individual determined by advantages it has over others

        • survives to bear offspring with same trait



The basis for natural selection l.jpg
The Basis for Natural Selection

  • There is much variation between members of a species.


The basis for natural selection29 l.jpg
The Basis for Natural Selection

  • There is much variation between members of a species

  • Reproduction is way in excess of the number that the habitat can survive

    e.g., Robins



The basis for natural selection31 l.jpg
The Basis for Natural Selection

  • There is much variation between members of a species

  • Reproduction is way in excess of the number that the habitat can survive

    e.g., Robins

    3. Differential reproductive success-those best adapted survive to reproduce the most



Theory of evolution33 l.jpg
Theory of Evolution

  • Darwin didn’t have all the tools we have today to explain his idea.

  • Genetics was in its infancy—Mendel’s ideas, though contemporary with Darin, weren’t appreciated for decades.

  • Genes-hereditary factors

  • Particulate inheritance

    • Gregor Mendel’s idea that organisms retain identities through generations

    • Peas

      • No blending

      • Colors could be masked for generations


Theory of evolution35 l.jpg
Theory of Evolution

  • Mutations

    • alteration of genes

    • provides for variability

    • very few are helpful

  • DNA

    • Deoxyribonucleic Acid

    • transmits chemically coded information

    • mostly found in chromosomes


Theory of evolution37 l.jpg
Theory of Evolution

  • sexual recombination

    • each parent contributes one half of its chromosomes to offspring via a gamete

      • special reproductive cell containing one of each type of chromosome

        • female ovum/egg; male sperm

    • yields new combinations-e.g., my kids aren’t exact copies of me; genes of their mother and me are both present.

      • mutations increase variability—and we all have them!

  • gene pool

    • sum total of genetic components of a population or group of interbreeding individuals

    • you have only a small subset of the human gene pool

      • reproductive barriers limit the pool and keep species separate

  • speciation

    • origin of a new species from two or more individuals of a preexisting species


Reproductive isolation l.jpg
Reproductive Isolation

Fall breeder

Spring breeder


Origination l.jpg
Origination

  • Evolutionary radiations

    • pattern of expansion from some ancestral adaptive condition represented by descendant taxa

  • adaptive breakthrough

    • appearance of key features that allow radiation to occur

  • fossil record documents patterns

    • E.g., Jurassic corals



Origination41 l.jpg
Origination

  • Rates of speciation

    • Galápagos Islands-formed millions of years ago

    • Lake Victoria

      • 13,000 years old

      • 497 unique species of cichlid fish, many with specialized adaptations

  • Molecular clock

    • assume average rate of mutation

    • determine pace of change

    • extrapolate timing of change


Convergence l.jpg
Convergence

  • Evolution of similar forms in two or more different biological groups

  • Marsupials and placental mammals

    • similar form

    • isolated, adaptive convergent evolution after initial divergence


Extinction l.jpg
Extinction

  • caused by extreme impacts of limiting factors

    • predation

    • disease

    • competition

  • pseudoextinction

    • species evolutionary line of descent continues but members are given a new name

  • high rates of extinction make useful index fossil

    • ammonoids


Extinction44 l.jpg
Extinction

  • rates

    • average rate has declined through time

  • mass extinctions

    • many extinctions within a brief interval of time

    • largest events peak at extinction of >40% genera

    • rapid increase (radiation) follows


Modern mass extinctions l.jpg
Modern Mass Extinctions

  • fossil patterns reflected in modern

    • tropical species

    • large animals

  • loss of habitat

  • direct exploitation

  • likely replacement by opportunistic species


Evolutionary trends l.jpg
Evolutionary Trends

  • Cope’s rule

    • body size increases during evolution of a group of animals

    • structural limitations on size

  • specialized adaptations limit evolution

    • elephants

    • manatees


Evolutionary trends47 l.jpg
Evolutionary Trends

Whales

  • terrestrial origin

    • 50 Ma

    • small (2 m) mammals with feet

  • marine adaptation

    • 40 Ma

    • lost hind limbs

    • no pelvic bones

    • up to 20 m


Phylogeny l.jpg
Phylogeny

  • Phylogeny

    • complex, large-scale trend within a branching tree of life

    • gradual large-scale change from one species to another is rare

      • e.g., Jurassic coiled oysters


Phylogeny49 l.jpg
Phylogeny

  • Axolotl

    • example of rapid speciation from parent species

      • parent is amphibious

      • offspring is aquatic throughout life after one simple genetic change


Phylogeny50 l.jpg
Phylogeny

  • rates

  • gradualistic model

    • very slow rates

  • punctuational model

    • rapid evolution with little change between steps

    • bowfin fish

      • little change in 60 m.y.


Phylogeny51 l.jpg
Phylogeny

  • Horses

    • increase in body size

    • evolved tall complex molars and single-hoofed toe

    • change driven by climate

      • expansion of grasslands

  • Dollo’s law

    • evolutionary transition from at least several genetic changes is highly unlikely to be reversed by subsequent evolution


ad