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Evolution - PowerPoint PPT Presentation

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Evolution. Key Points. Heritable characteristics increase or decrease an organisms chance of survival Evolution is the change of the genetic makeup of a population over time More closely related organisms have more closely related DNA and proteins

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Key points
Key Points

  • Heritable characteristics increase or decrease an organisms chance of survival

  • Evolution is the change of the genetic makeup of a population over time

  • More closely related organisms have more closely related DNA and proteins

  • Many organisms have similar structures, and many organisms develop similarly

Key points1
Key Points

  • Mutations that lead to evolution occur randomly

  • All species on earth are related by a common ancestor

  • The fossil record shows organisms that are no longer alive

  • Environmental pressures, genetic drift, mutation and competition for resources lead to evolution

How did life on earth begin
How did life on earth begin?

  • There are many theories

  • Information about early earth comes from rocks

  • The earth is ~4.6 billion years old

  • The oldest clues about life on earth are ~3.5 billion years old


  • Fossils are preserved evidence of organisms

  • 99.9% of all organisms are extinct

  • Very few organisms become fossilized

  • Many fossils are casts

    • Minerals fill in the areas where the organism was

Dating methods
Dating Methods

Relative Dating

  • A technique where items (rocks or fossils) are dated by comparing the soil layers

  • The Law of Superposition

    • Sedimentary rock is deposited in layers

    • Older layers are deeper

    • Newer layers are on top

  • Explain the picture?

Dating methods1
Dating Methods

Radiometric Dating

  • Uses radioactive isotopes to date rocks or organic material

    • Uses the half life of the isotope

  • Carbon-14

    • Decays to Nitrogen-14

    • Half life is 5730 years

    • Can date organisms up to 50,000 years

  • Potassium-40

    • Used to date older items

    • Can only be used to date rocks

    • Half life is 1.3 Billion years

Geologic time
Geologic Time

  • Represents major geologic events

Spontaneous generation a hypothesis
Spontaneous Generation-A Hypothesis

  • Spontaneous generation- life arises from no life

    • Francisco Redi’s experiment

    • Redi’s experiment opposes the hypothesis

Biogenesis a theory
Biogenesis- a theory

  • Biogenesis- life arises from life

  • Louis Pasteur – biogenesis is true for microorganisms

Origins of life
Origins of Life

  • Simple organic molecule formation

  • Organic molecules could be synthesized by simple reactions

  • UV light from the Sun and lightning may have been the primary energy source

Miller and urey
Miller and Urey

  • Simple organic molecules are made from inorganic molecules

  • Conditions were like that of early earth

  • Prokaryotes evolved first

    • Archea most closely resemble earth’s first life

    • They are autotrophs, energy does not come from the sun, they do not need oxygen

  • Photosynthesizing prokaryotes evolved next

    • Oxygen was just a byproduct

  • Eukaryotes evolved by prokaryotes developing symbiotic relationships

Darwin natural selection
Darwin & Natural Selection

  • Darwin was a naturalist on the HMS Beagle

    • He was also a companion to the captain

    • He collected biological samples

  • Darwin collected many birds, mockingbirds and finches on the Galapagos Islands

    • Each island had similar birds, but they were slightly different

Artificial selection and natural selection
Artificial Selection and Natural Selection

  • Humans could changes species such as dogs by artificial selection

  • Darwin’s Hypothesis

    • New species could appear gradually through small changes in ancestral species

Natural selection
Natural Selection

  • Individuals in a population show variation

  • Variations are inherited

  • Organisms have more offspring than can survive on the available resources

  • Variations that increase reproductive success will have a greater chance of being passed on

Support for evolution
Support for Evolution

  • Fossils

    • Fossils show species that lived long ago

    • Ancient species share similarities with living species



Support for evolution1
Support for Evolution

  • Derived traits: newly evolved features that do not appear in common ancestors

    • Feathers

  • Ancestral traits

    • More primitive features that do appear in ancestral forms

Homologous structures
Homologous Structures

  • Anatomically similar structures inherited from a common ancestor

    • Structures are used for different purposes

Vestigial structures
Vestigial Structures

  • Structures that are reduced in form

    • They are useful in related organisms

  • Features of ancestors that are no longer useful will become smaller or lost over time

Analogous structures
Analogous Structures

  • Structures used for the same purpose but are not from a common ancestor

Comparative embryology
Comparative Embryology

  • Vertebrate embryos look very similar as embryos

  • Develop differently as they get older

Comparative biochemistry
Comparative Biochemistry

  • Common ancestry can be seen in metabolic molecules

    • DNA

    • Amino acid sequences

  • More closely related organisms have similar sequences

Genetic drift
Genetic Drift

  • Change in allele frequency

    • Caused by chance

    • Seen in small populations

Founder Effect

Population Bottleneck

The population almost goes extinct

A few surviving members survive and reproduce

  • A small sample of a population emigrate to a new area

  • Alleles that were uncommon in the parent population become popular

Gene flow
Gene Flow



  • Immigration and emigration

  • Increases variation within a population

  • Promotes inbreeding

  • Can cause alleles frequency to change

  • Female is usually choosey

  • Male usually displays traits

Types of selection
Types of Selection

  • The best suited individuals survive

  • Derive a situation that could cause each graph.

Human evolution
Human Evolution

  • What is a primate (Ape)

    • Manual dexterity

    • Flexible bodies

    • Limber shoulders and hips

    • Large Brain

    • Can solve problems

    • Social

    • Newborns dependent on mother

    • Have fewer offspring

  • Are you an ape?


  • Bipedalism- changing environment

  • Large Brain- evolved after bipedalism