Exam 4

What is evolution?

• change in populations of from generations to generations

• changes to genes lead to modified behavior appearance/behavior

History of Evolutionary though

Jean-Baptiste Lamarck

• use and disuse

• inheritance of acquired characteristics

Who was Charles Darwin?

• Born 1809; wealthy family

• father wanted him to be a doctor, but Charles liked plants and animals more

What “current” ideas influenced Darwin?

Charles Darwin (1809-1882)
• Existing knowledge that variation occurred among organisms
• Charles Lyell – geologist – uniformitarianism (geological processes
that go on today are also what shaped the earth in the past → old earth)
• Thomas Robert Malthus – economist – populations over-reproduce
(beyond sustainability → some will die)
• 5-year voyage of the Beagle

The voyage of the Beagle

12/21/1831 - 10/02/1836

Darwin observed finches

What were Darwin’s conclusions?

• More offspring are often produced than can survive
  (resources are limited)

• Traits vary among individuals (phenotypes)

• Different traits affect survival/reproduction differently

• Traits are passed to offspring

• Future populations will have more individuals from parents
  with traits that allowed them to survive/reproduce better

• NATURAL SELECTION!

What did Darwin do after his trip?

• Charles Darwin (1809-1882)

• Return of the Beagle (1836)
  → On the Origin of Species by
  Means of Natural Selection
  (1859)

What did Alfred Russell Wallace do?

• he embarked on a similar journey to Darwin and came to the same conclusions

• he submitted his work to Darwin which led to Darwin publishing his work

What are the five steps of evolution by natural science?

1. Genetic Variation

2. Selection Pressure

3. Overproduction

4. Differential Success

5. Repeat

Genetic Variation

• individuals of a specific species vary in their characteristics

Selection Pressure

• organisms face a constant struggle to survive and reproduce

Overproduction

• More offspring are produced than can survive to maturity

Differential Success

• Variation causes some individuals to outperform others

Fitness

• survival - feeding/growth - successfully - reproduce - young service

• being able to fit and reproduce

Directional Selection

• phenotype at the end of the range of variation is favored

• ex: evolution of moth colour; white is more easily spotted than black

Stabilizing Selection

• middle, intermediate chosen

• ex: human birth weight

Disruptive Selection

• Phenotypes on either end of range of variation are favored – intermediate phenotypes are selected against

• ex: seedcraker birds

Artificial Selection vs Natural Selection

Artificial Selection

• based on human preferences

Natural Selection

• based on fitness: survival and reproduction

Artificial Selection

• “human preferences”

• Darwin used humans use of selective

Causes of Evolution

• Natural/Artifical Selecton - not random

• Mutation - random

• Genetic Drift - random

• Gene Flow - random

Mutation

• Change in DNA

• permanent

• source of new alleles

• 70 mutations per person

• Arise all the time

• Limited by mitosis checkpoints

Genetic Drift

• Things happen by chance

• individual mortality

• finding a mate

• which gametes fertilize

• Small populations are at greater risk

What magnifies genetic drift?

• bottleneck effect

• founder effect

Migration

• Also called gene flow

• Exchange of genes between two different populations

• introduction of genes

What evidence do we have for evolution?

• fossils

• molecular biology

• biogeography

• anatomy and embryology

• genes regulate the development in the same way in related organisms

Population

organisms of same species

Species

group of organisms capable of interbreeding and capable of producing viable offspring

How do biologists define space?

• not always appearance

• reproductive compatibility

• ability to interbreeding/mate and produce visible, fertile offspring

Speciation

• overtime and some sort of isolation, the variation among sub-populations becomes so great they can no longer interbreed and they become tow different species

How does speciation happen?

1. allopatric speciation

2. sympatric speciation

Allopatric Sepciation

geographic isolation

Sympatric Speciation

same geographic area

“Evolution is just a theory”

• theory in science is different

• scientists have theories on gravity, atoms, etc.

“Evolution explains origin of life”

• evolution describes the origin of species, not origin

“Individual evolve”

• individuals can’t change their genetic makeup

• populations change over generations

“Organisms evolve on purpose”

• evolution is not intentional

• variation already exists in the population, it does not arise due to need

“Evolution is controversial among scientists”

• proposed in 1859

• accepted by scientists within 20 years

• why?

• Darwin had accumulated so much evidence

• supernatural explanations can not be tested by science

How do we organize life or earth?

• evolutionary relationships between organisms are shown with branching diagrams: phylogenetic trees

• they show scientists best estimates of evolutionary history

• phylogenetics trace patterns of shared ancestry between lineage

• each lineage has a part of it’s history that is unique to it alone and parts that are shared with other lineage

• ancestors that are unique to that lineage and ancestors that are shared with other lineages

How are phylogenetic trees made?

• they are based on analyzing traits and grouping organisms based on shared and derived traits

How do you refer to different species?

• taxonomy ( naming ) should follow phylogeny (evolutionary relationships)

• both are hierarchical

1. Domain

2. Kingdom

3. Phylum

4. Class

5. Order

6. Family

7. Genes

8. Species

9. Subspecies

How do scientists name species?

• Every organism has 2-part-name

• genes - species

• Rules for Binomial Nomenclature

• 1st name = Genus, capitalized

• 2nd name = species, lowercase

• Latin

• underlined if written

• italicized if typed

Carl Linnaeus

Father of Taxonomy

Genus

group of species that share a set of traits

How do you read a phylogenetic tree?

• each branch point represents a common ancestor

• each taxon or group is united by shared characteristics

Sister Taxa

• more closely related to each other than any other taxon on the tree

• share branch point

• did NOT evolve from each other but from common ancestor

Misconceptions about humans

• did not evolve from chimps: share common ancestor

• humans are not higher/more evolved than other

Remember: evolutional is directional, not goal-oriented, tree not a ladder