Evidence for EvolutionWas Darwin Wrong?
Thursday, May 1st
EVOLUTION
• It does not mean random
• It does not mean to improve
• It does not mean morphing during a lifetime
• It does not mean abiogenesis
• It means CHANGE OVER TIME
What is “fitness”?
• What does it mean to be “fit”?
–To be able to survive AND reproduce
The table below gives descriptions of four female mice that live in a beach area which has mostly tan sand with scattered plants.
According to the definition given for fitness, which mouse would
biologists consider the fittest? Explain why this mouse would be the fittest...
Fur color Black Tan Tan and Black
Cream
Age at death
2 months 8 months 4 months 2 months
# pups produced by each female
0 11 3 0
Running speed
8 m/min 6 m/min 7 m/min 5 m/min
What is “fitness”?
• What does it mean to be “fit”?
–To be able to survive AND reproduce offspring that can THEN reproduce
*
Below are descriptions of 4 male lions. According to our newest definition of fitness, which lion would
biologists consider the “fittest”?
Name George Brian Spot Bob
Age at death
13 yrs 16 yrs 12 yrs 10 yrs
# of cubs fathered
19 25 20 20
# of cubs surviving to adulthood
15 14 14 19
Size 10 ft 8.5 ft 9 ft 9 ft
Natural Selection vs Evolution
• Evolution • = The change in the
inherited characteristics of biological populations over successive generations
• Natural selection• = It is a key
MECHANISM of evolution
• is the only known cause of adaptation, but not the only known cause of evolution
*
Who was Charles Darwin?
• English naturalist
• Evolution resulted from natural selection– The struggle for existence
is SIMILAR to artificial selection and selective breeding
• Dog breeds• Beef cattle
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HMS The Beagle
The 4 Components of NS• 1. Variation = exists among individuals in a population of
species
• 2. Inheritance = Some traits are consistently passed on from parent to offspring.
• 3. Population growth = Most populations have more offspring each year than local resources can support leading to a struggle for resources.
• 4. Survival of the Fittest = Individuals with advantageous variations will be more likely to survive and reproduce
*
Who was Charles Darwin?
• Process of natural selection:
– Populations of organisms can evolve if individuals having certain heritable traits leave more offspring than others
• Variations = adaptations:– Inherited characteristics
that enhance organisms’ survival and/or reproduction
November 24, 1859
*
Who was Charles Darwin?
• Cladistics– Hierarchical classification of species
based on evolutionary ancestry
– Cladograms = Evolutionary “Tree of Life”
– Makes no distinction between extinct and non-extinct species
• Appropriate to include extinct species in the group of organisms being analyzed
*
Cat, lion, seal & human
Who influenced Darwin?• Carolus Linnaeus (1750’s)
– Taxonomy (scientific groupings/names)– Used latin as the universal language
• Ex: Canis lupis – wolf• Ex: Homo sapien - human
• Jean-Bapiste Lamarck (1800)– Organisms change through use and disuse– Inheritance of acquired characteristics– Environments are what cause organisms to
change
Who influenced Darwin?• James Hutton (1785)
– Gradualism (rock formations - SLOW)
– Earth was transformed by imperceptibly slow changes• So natural selection/evolution could be really slow too
• Charles Lyell (1830’s)– Principal of Uniformitarianism
– Geological forces at work in the present day = same as those that operated in the past
– The past can be found in the present
What is the Evidence for Evolution?
• Paleontology– Investigates extinct life-forms as
revealed in the fossil record
• We call this FOSSIL EVIDENCE
• Classifying ancient organisms is difficult– Many do not “fit” well into the modern
form of taxonomy (Classification)
What is the Evidence for Evolution?
• DNA is made of 4 nucleotides• Adenine, thymine, cystosine and guanine
– Everything living is made of the same material, it’s just rearranged differently
• We call this MOLECULAR EVIDENCE
What is the Evidence for Evolution?
• You can trace similarities as far back as the beginning
– All fungi, plant and animal cells have nuclei
– All living organisms have RNA and DNA
What is the Evidence for Evolution?
• Biogeography
– The study of the geographical distribution of living creatures• Which species inhabit which parts of the planet
and why?
– Closely related species tend to be found:• On the same continent (similar species of zebra)• Or within the same group of oceanic islands (diff.
finches on the Galapagos Islands)
What is the Evidence for Evolution?
• Isolation + Time + Adaptations to local environmental conditions = new species
What is Comparative Anatomy?
The science of anatomical shape and design
• An organism’s body structure – Called its “basic plan”
• We call this ANATOMICAL EVIDENCE
• Can you guess what is similar between all of the organisms on the next slide?
What is Comparative Anatomy?
• All of these organisms have an INTERNAL skeleton
What is Comparative Anatomy?
• Homologous structures
– Similar structures that related species have inherited from a common ancestor
– Ex: Paired bones of the lower leg (tibia and fibula) can be traced back to the 1st “bird”, Archaeopteryx
What is Comparative Anatomy?
• Analogous vs Homologous
• Wings– Maple seed– Albatross – Analogous
• Both allow the organism to travel on the wind– Both did not develop from the
same structure
What is Comparative Anatomy?
• Vestigial structures– Structures that have lost most of their
original function in a species through evolution
– Appear to serve no useful function
• Examples:– Snakes: tiny pelvic bones & limb bones– Flightless beetles: have wings sealed that
never open
What is Comparative Anatomy?
• Vestigial organs are often exactly the same as organs that are useful in other species– Our tailbone is homologous to the
functional tail of other primates
– Organisms having vestigial structures probably share a common ancestry with organisms that have use for the organ.
What is Comparative Anatomy?
What is Comparative Anatomy?
• Embryology
– Examines the revealing stages of development that embryos pass through before birth or hatching
– Many organisms look extremely similar when developing in the womb
What is Comparative Anatomy?
• Embryonic structures can be adapted to different ultimate uses, for example, pharyngeal arches ("gill slits")– fish gill cartilage, the
reptilian jaw, and the mammalian middle ear
• Developmental ancestry: structures arise from the same tissue in embryonal development
What are the different types of evolution?
• Divergent– Adaptive radiation
• 2 or more related species become more and more dissimilar
• Adapting to different environments–Kit fox plains & deserts (sandy
colored fur & large ears)–Red fox mixed farmlands & forests
(red fur)
What are the different types of evolution?
• Convergent– Unrelated species become more and more
similar in appearance– Adapting to the same kind of environment– Creates analogous structures
• Example – wings of–Pteranodon–Bats–Birds
What are the different types of evolution?
• Co-evolution the evolution of 2 species totally dependent on each other
– An explosion of insect diversity seemed to correlate with the abundance of flowering plants.
• Angiosperms (flowering plants) depend on pollinating insects in order to survive and the insects depend on flowers for food.
What are the different types of evolution?
• Gradualism– Change is SLOW, CONSTANT &
CONSISTENT– Selection & variation occur more gradually– Over a short period of time, it’s hard to notice– Very gradually, over a long period of time, the
population changes
What are the different types of evolution?
• Punctuated equilibrium– CHANGE COMES IN SPURTS– Predicts that a lot of evolutionary change
takes place in short periods of time – Speciation is likely to occur at the edge of a
population• Where a small group can become separated
geographically from the main body population
So what is evolution anyway?
• It’s not necessarily a DECISION – the organisms that are best at surviving will produce babies (offspring)
• The organisms that cannot survive… well, they can’t really have offspring if they’re dead, right?
• We call that NATURAL SELECTION or Survival of the Fittest – Only the fit survive and reproduce – mutations that
affect an organism prior to reproduction tend to get “eliminated”
Evidence for Evolution
THE TOP EIGHT8. Wings on flightless birds
– Ostriches– Emus– Kiwi
7. Hind leg bones in whales– Baleen and humpback whales
Evidence for Evolution
6. Erector pili and body hair– When you get scared, your hair stands on end– When mammals get scared, it makes them
look BIGGER
5. The human tailbone– Was once used for balance, communication
(think dogs) or a prehensile limb
Evidence for Evolution
4. Wisdom teeth in humans– Gorillas have these teeth to help chew and
grind food– We brush our teeth, so we don’t lose our teeth
as often
3. Whiptail lizards– There are ALL female!– These lizards literally clone themselves
Evidence for Evolution
2. Male breast tissue and nipples
– This tissue is not functional, although a small percentage of males have been able to lactate
– ALL mammals, male and female, have mammary glands
– Males can also contract breast cancer
Evidence for Evolution
1. The Human Appendix
– In herbivores, the appendix helps by breaking down plant material for digestion
– Unfortunately, this organ no longer helps us with digestion what so ever
– In 2006, over 300,000 appendectomies were performed in the United State and over 400 people have died from appendicitis.