evolution and the origin of life

1. Evolution and theEvolution and the
Origin of LifeOrigin of Life

2. ORIGINS OF LIFEORIGINS OF LIFE
 1 billion years of chemical change to form1 billion years of chemical change to form
the first cells, followed by about 3.7 billionthe first cells, followed by about 3.7 billion
years of biological changeyears of biological change
Figure 4-2Figure 4-2

3. Biological EvolutionBiological Evolution
 Explained by Charles Darwin and AlfredExplained by Charles Darwin and Alfred
Russell WallaceRussell Wallace
Darwin
Wallace

4. BiologicalBiological
EvolutionEvolution
 This has led toThis has led to
the variety ofthe variety of
species wespecies we
find on thefind on the
earth todayearth today
 8 – 100 million8 – 100 million
speciesspecies
Figure 4-2Figure 4-2

5. Natural SelectionNatural Selection
 Natural selectionNatural selection – the mechanism of– the mechanism of
evolution – how evolution worksevolution – how evolution works
 Some individuals have genetically based traitSome individuals have genetically based trait
that increase their chances of survival andthat increase their chances of survival and
their ability to produce offspring with thetheir ability to produce offspring with the
same traitssame traits

6. How Do We Know Which OrganismsHow Do We Know Which Organisms
Lived in the Past?Lived in the Past?
 Our knowledgeOur knowledge
about past lifeabout past life
comes from fossils,comes from fossils,
chemical analysis,chemical analysis,
cores drilled out ofcores drilled out of
buried ice, and DNAburied ice, and DNA
analysisanalysis
 Fossil record isFossil record is
incompleteincomplete

7. EVOLUTION, NATURALEVOLUTION, NATURAL
SELECTION, AND ADAPTATIONSELECTION, AND ADAPTATION
 Biological evolution by natural selectionBiological evolution by natural selection
involves the change in a population’s geneticinvolves the change in a population’s genetic
makeup through successive generationsmakeup through successive generations

Genetic variabilityGenetic variability

MutationsMutations – random changes in the structure or– random changes in the structure or
number of DNA molecules in a cell that can benumber of DNA molecules in a cell that can be
inheritedinherited by offspringby offspring
 Evolution occurs in populationsEvolution occurs in populations
 Natural selection acts on individualsNatural selection acts on individuals

8. Natural Selection and Adaptation:Natural Selection and Adaptation:
Leaving More Offspring WithLeaving More Offspring With
Beneficial TraitsBeneficial Traits
 Three conditions are necessary for biologicalThree conditions are necessary for biological
evolution:evolution:

Genetic variability, traits must be heritable, traitGenetic variability, traits must be heritable, trait
must lead tomust lead to differential reproductiondifferential reproduction
 AdaptationAdaptation – (adaptive trait) – any heritable– (adaptive trait) – any heritable
trait that enables an organism to survivetrait that enables an organism to survive
through natural selection and reproducethrough natural selection and reproduce
better under prevailing environmentalbetter under prevailing environmental
conditionsconditions

9. Natural Selection and Adaptation:Natural Selection and Adaptation:
Leaving More Offspring WithLeaving More Offspring With
Beneficial TraitsBeneficial Traits
 Genetic resistanceGenetic resistance – ability of organisms in– ability of organisms in
a population to tolerate a chemical designeda population to tolerate a chemical designed
to kill itto kill it

10. How Did Humans Become Such aHow Did Humans Become Such a
Powerful Species?Powerful Species?
 We lackWe lack

Strength, speed, agilityStrength, speed, agility

Weapons (claws, fangs), protection (shell)Weapons (claws, fangs), protection (shell)

Poor hearing and visionPoor hearing and vision
 Three adaptations have helped the humanThree adaptations have helped the human
speciesspecies

Strong opposable thumbsStrong opposable thumbs

The ability to walk uprightThe ability to walk upright

Complex brainComplex brain

11. Adaptation Has LimitsAdaptation Has Limits
 Adaptive genetic traits must precede changeAdaptive genetic traits must precede change
in the environmental conditionsin the environmental conditions
 A population’s reproductive capacityA population’s reproductive capacity

Species that reproduce rapidly and in largeSpecies that reproduce rapidly and in large
numbers are better able to adaptnumbers are better able to adapt

12. Myths About EvolutionMyths About Evolution
 Fitness is reproductive success, not strengthFitness is reproductive success, not strength
 Organisms do not develop traits out of needOrganisms do not develop traits out of need
or wantor want
 There is no grand plan of nature for perfectThere is no grand plan of nature for perfect
adaptationadaptation

13. If environmental conditions change,If environmental conditions change,
species can:species can:

AdaptAdapt

MigrateMigrate

Become extinctBecome extinct

14. Coevolution: A Biological Arms RaceCoevolution: A Biological Arms Race
 Interacting species – a back and forth geneticInteracting species – a back and forth genetic
contest in which each gains a temporarycontest in which each gains a temporary
genetic advantage over the othergenetic advantage over the other
 CoevolutionCoevolution – interaction where changes in– interaction where changes in
gene pool of one species can lead togene pool of one species can lead to
changes in the gene pool of the otherchanges in the gene pool of the other
speciesspecies

This often happens between predators and preyThis often happens between predators and prey
species.species.