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EVOLUTION & SPECIATION

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EVOLUTION & SPECIATION. VOCABULARY REVIEW. EVOLUTION – CHANGE OVER TIME NATURAL SELECTION - INDIVIDUALS BETTER ADAPTED TO THE ENVIRONMENT ARE ABLE TO SURVIVE & REPRODUCE. A.K.A. “SURVIVAL OF THE FITTEST”. NEW VOCABULARY. POPULATION – GROUP OF INDIVIDUALS OF SAME SPECIES THAT INTERBREED

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Presentation Transcript
vocabulary review
VOCABULARY REVIEW
  • EVOLUTION – CHANGE OVER TIME
  • NATURAL SELECTION - INDIVIDUALS BETTER ADAPTED TO THE ENVIRONMENT ARE ABLE TO SURVIVE & REPRODUCE.
    • A.K.A. “SURVIVAL OF THE FITTEST”
new vocabulary
NEW VOCABULARY
  • POPULATION – GROUP OF INDIVIDUALS OF SAME SPECIES THAT INTERBREED
  • GENE POOL – COMMON GROUP OF ALL GENES PRESENT IN A POPULATION
gene pool
Gene Pool

Combined genetic info. of all members

Allele frequency is # of times alleles occur

variation in populations
Variation in Populations

2 processes can

lead to this:

Mutations -

change in DNA

sequence

Gene Shuffling –

from sexual

reproduction

genetic drift changes populations
Genetic Drift changes populations…….
  • Random change in allele frequency causes an allele to become common
slide8
Founder Effect: a cause of genetic drift attributable to colonization by a limited number of individuals from a parent population
slide9
Gene Flow: genetic exchange due to the migration of fertile individuals or gametes between populations (reduces differences between populations)
slide10
Nonrandom mating: inbreeding and assortive mating (both shift frequencies of different genotypes)
slide11
Natural Selection: differential success in reproduction; only form of microevolution that adapts a population to its environment
sexual selection
Sexual selection
  • Sexual dimorphism: secondary sex characteristic distinction
  • Sexual selection: selection towards secondary sex characteristics that leads to sexual dimorphism
evolution of populations
Evolution of Populations

Occurs when there is a change in relative frequency of alleles

phenotype expression
Phenotype Expression
  • Depends on how many genes control that trait
single gene vs polygenic traits
Single-Gene vs. Polygenic Traits

(EG: tongue rolling)

Single-Gene:

2 Distinct Phenotypes

Polygenic:

Many Phenotypes

natural selection on polygenic traits
Natural Selection on Polygenic Traits
  • Shifts to

middle range

  • Shifts to

2 extremes

  • Shifts to

1 extreme

speciation
SPECIATION
  • THE FORMATION OF NEW SPECIES
  • AS NEW SPECIES EVOVLVE, POPULATIONS BECOME REPRODUCTIVELY ISOLATED
  • REPRODUCTIVE ISOLATION – MEMEBERS OF 2 POPULATIONS CANNOT INTERBREED & PRODUCE FERTILE OFFSPRING.
3 isolating mechanisms
3 ISOLATING MECHANISMS……..
  • BEHAVIORAL ISOLATION- CAPABLE OF BREEDING BUT HAVE DIFFERENCES IN COURTSHIP RITUALS (EX. MEADOWLARKS)
  • GEOGRAPHICAL ISOLATION – SEPARATED BY GEOGRAPHIC BARRIERS LIKE RIVERS, MOUNTAINS, OR BODIES OF WATER (EX. SQUIRREL)
  • TEMPORAL ISOLATION – 2 OR MORE SPECIES REPRODUCE AT DIFFERENT TIMES.
slide28

Tigon

Result of male tiger and female lion mating incaptivity. Offspring are infertile.

Separated both geographically and ecologically.

liger
Liger

Result of male lion and female tiger mating in captivity. Offspring are infertile.

fig 23 6
Fig. 23.6

Four species of leopard frogs: differ in their mating calls. Hybrids are inviable.

slide36

These squirrels live on opposite sides of the Grand Canyon. This is an example of allopatric speciation.

hawaiian honeycreepers
Hawaiian Honeycreepers

An example of adaptive radiation –

these species all diverged from a

common ancestor (founder species)

FOUNDER SPECIES

speciation in darwin s finches
SPECIATION IN DARWIN’SFINCHES
  • SPECIAITON IN THE GALAPAGOS FINCHES OCCURRED BY:

- FOUNDING OF A NEW POPULATION,

- GEOGRAPHIC ISOLATION which led to -- REPRODUCTIVE ISOLATION and

CHANGES IN THE NEW POPULATION’S GENE POOL due to COMPETITION.

evidence of evolution
Evidence of Evolution
  • Fossil Record
  • Geographic Distribution of Living Species
  • Homologous Body structures
  • Similarities in Embryology
slide42

Evidence of

Evolution

Fossil Record provides evidence that living things have evolved

Fossils show the history of life on earth and how different groups of organisms have changed over time

slide46

Flying Squirrel

Sugar Glider

Marsupial Mammals

Convergent Evolution

and

AnalogousStructures

Placental mammals

Mammalia

Rat like common ancestor

slide48

Big Question!!!

  • How did life arise on the big blue planet??
  • Scientists attempt to answer this question scientifically.
relative dating
Relative Dating
  • Can determine a fossil’s relative age
  • Performed by estimating fossil age compared with that of other fossils
  • Drawbacks – provides no info about age in years
absolute dating
Absolute dating
  • Can determine the absolute age in numbers
  • Is performed by radioactive dating – based on the amount of remaining radioactive isotopes remain
  • Drawbacks - part of the fossil is destroyed during the test
slide54

Big Bang Theory

  • A cosmic explosion that hurled matter and in all directions created the universe 10-20 billion years ago
  • Evidence
    • it explains why distant galaxies are traveling away from us at great speeds
    • Cosmic radiation from the explosion can be observed
  • The Big Bang theory probably will never be proven; consequentially, leaving a number of tough, unanswered questions.
slide55

What was early earth like?

  • Earth was Hot!!
  • Little or no oxygen
  • Gasses in atmosphere:
    • Hydrogen cyanide (poison to you!)
    • Hydrogen sulfide
    • Carbon dioxide
    • Carbon monoxide
    • Nitrogen
    • water
slide56

So how did the earth get oxygen?

  • Some of that oxygen was generated by photosynthetic cyanobacteria
  • Some came from the chemical separation of water molecules into oxygen and hydrogen.
slide57

Oxygen drove some life forms to extinction

  • Others evolved ways of using oxygen for respiration
slide58

How did life begin?

Miller and Urey’s Experiment

  • Passed sparks through a mixture of hydrogen methane ammonia and water
  • This produced amino acids – the building blocks of life
slide60

How can simple amino acids result in life? There are 3 theories

1. Formation of microspheres

  • Large organic molecules can sometimes form tiny proteinoid microspheres
  • Store and release energy, selectively permeable membranes, may have acquired more characteristics of living cells
slide61

2nd Hypothesis for Life

Evolution of RNA to DNA

  • RNA was assembled from simple organic molecules in a primordial soup
  • RNA was able to replicate itself and eventually form DNA
  • Not scientifically proven to be possible
slide62

3rd Theory of Life

Endosymbiotic theory

  • eukaryotic cells arose from living communities formed by prokaryotic organisms
  • Ancient prokaryotes entered primitive eukaryotic cells and remained there as organelles
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