Evolution

The quick view (which is opposite of how evolution works, so it’s kind of ironic eh?)

Science vs. Religion

u  What is science based on?

u  Science is based on OBSERVABLE evidence.

u  What is religion based on?

u  Religion is based on FAITH.

–   By definition, faith is something that is not observable.

u  Since they are 2 different “fields,” they aren’t really competing with each other

 

Religious Scientists?

u    My religion consists of a humble admiration of the illimitable superior spirit who reveals himself in the slight details we are able to perceive with our frail and feeble mind.   

–    Albert Einstein (1879 - 1955)

u    Science without religion is lame, religion without science is blind.

–    Albert Einstein (1879 - 1955), "Science, Philosophy and Religion: a Symposium", 1941

u    Not only does God play dice, but... he sometimes throws them where they cannot be seen.

–    Stephen Hawking

Evolution is a Theory

u  To paraphrase Carl Sagan:

–  Creationists think that a theory is something that you made up while drunk one night.

u   Theory Defined: “scientific principle to explain phenomena: a set of facts, propositions, or principles analyzed in their relation to one another and used, especially in science, to explain phenomena”

–    MSN Encarta, http://encarta.msn.com/dictionary_/theory.html

u   Evolution is as much a theory as gravity is

 

Ken Miller

u   He told us we could use the previous slides

u   www.millerandlevine.com

u   Thanks!

A Final Quote

uIn the immortal words, of “The Gru:”

–“Be opinionated, just not ignorant.”

Dating

u    Geologic Record

–    Hypothetical library of all the known geological processes on Earth

–    Determined through inference and dating methods

u    Relative Dating (hee hee)

–    Sediments are constantly being laid down.

–    Over time, many layers form

–    If a fossil is in a layer below a different fossil, it is older than that fossil

Dating

u    Radiometric Dating

–    Radioactive isotopes decay and form new isotopes  - the rate this happens is called the isotope’s half life

–    Ex: Potassium-40 decays to argon-40 and has a half life of 1.3 billion years

u  Half a sample will decay to argon-40 in 1.3 billion years

u  So if there are equal amounts of potassium-40 and argon-40 in an area, the sample has been in place 1.3 billion years

–    Carbon 14 has a half life of only 70,000 years for more recent sample dating

 

Review

•            How does the geologic record  help us?

•            What use is relative dating?

•            What is radiometric dating?

•            Why are different isotopes used in radiometric dating?

 

Charles Darwin

u    English naturalist (scientist) 1809-1882

u    1831, Darwin took a job as a naturalist on the HMS Beagle

–    Went on a 5-year scientific journey around the world

u    He collected many biological and fossil speciments

–    Combined with his previous and subsequent observations

u    Published On the Origin of Species by Natural Selection in 1859

–    These ideas are a basic unifying theme of biology today

–    Without evolution, biology doesn’t make as much sense

Selection

u    Artificial selection

–    Breeding organisms with specific traits in order to produce offspring with identical traits

u    Natural selection

–    A mechanism for change in populations

–    Occurs when organisms with favorable traits survive, reproduce and pass their traits on to the next generation

u  Organisms with these traits are said to be more “fit”

u  Organisms without these traits are less likely to survive and reproduce

Adaptations

u    Adaptation

–    Evolution of a structure, behavior, or internal process that enables an organism to respond to environmental factors and live to produce offspring

–    Can also be the structure itself

u    Structural adaptations take a long time

u    Physiological adaptations can happen faster

–    Bacteria strains develop resistances to antibiotics fairly quickly

Evidence for Evolution

u   Fossil Record

–   A hypothetical “library” of all the fossils collected around the world

u   Fossils show changes throughout time

–   99 percent of all animals are now extinct

–   Fossil record shows ancestors with similar characteristics

Evidence For Evolution

u     Anatomy

u     Homologous Structures are structural features with a common evolutionary origin

–    Ex: whale forelimb, crocodile forelimb, bird wing, human forelimb all look the same (p. 401)

–    Can you think of other examples?

u     Analogous Structures are body parts or organisms that do not have a common evolutionary origin but are similar in function

–    Bird, bat and butterfly wings

–    Show how organisms adapt to different ways of life and different conditions

 

Evidence for Evolution

u   Vestigial Structures are body structures that no longer serve their original purpose, but was probably useful to an ancestor

–   Ex: human appendix, pelvic bone in baleen whale, “tail” in humans, some human’s ability to wiggle their ears

Evidence for Evolution

u   Embryology – study of embryos of different species

u   Many species share features in the young embryos

–   Ex: Mammals, reptiles, birds and fish all have a tail and pharyngeal pouches (develop into different respiratory systems)

Evidence for Evolution

u   Biochemistry

u   Nearly all organisms share DNA, ATP, and many enzymes among their biochemical molecules

u   Organisms that share more similar enzymes, DNA sequences, etc. are more closely related

Human vs. Chimp Chromosomes

Other Hominids

Other Forms of Evidence

u   All primates need to “ingest” vitamin C because we can’t make it like we do Vitamin D

u   But, we do have 7 the genes to produce vitamin C

–   The 7^th one is turned off in all primates

–   A mutated one was probably passed on because it provided no disadvantage due to fruit diets

 

Review

•             How did Darwin come up with his ides for natural selection?

•             Some snakes have vestigial legs. Why is this considered evidence for evolution?

•             Explain how adaptations such as camouflage help species survive.

•             How do homologous structures provide evidence for evolution?

•             Why did birds and bats both get wings?

•             A parasite that lives in red blood cells causes the disease called malaria. In recent years, new strains of the parasite have appeared that are resistant to the drugs used to treat the disease. Explain how this could be an example of natural selection occurring.

Population Genetics

u   Populations evolve, not individuals

u   Natural selection acts on a range of phenotypes in a population

–   Genetic variation video

u   Evolution is often defined as a change in the frequency of an allele in a population over time

 

Population Genetics

u   All of the population’s genes are in a theoretical “gene pool”

u   The percentage a specific allele in the gene pool is called the allelic frequency

u   A population in which the frequency of alleles remains relatively the same over generations is in genetic equilibrium

u   Any change in this genetic equilibrium results in evolution

Hardy-Weinberg Principle

u          How to Stop Evolution – must meet all five requirements

•             Population is so large, chance alone cannot change relative frequency (genetic drift doesn’t occur)

•             Mutations do not occur

•             All genotypes have equal fitness (no natural selection)

•             No organisms leave or enter a population

•             Mating occurs at random

 

Mutations

u   Mutation provides the raw material for evolution to act upon

–   Poor mutations are selected against, good mutations are selected for

–   Change the frequency of alleles

–   Examples:

u   Sometimes mutations are a compromise:

–   L4 & L5 in your backbone – poor design, but needed to stand upright

 

 

Genetic Drift

u   Genetic drift is the alteration of allelic frequencies by chance events

u   Genetic drift can greatly affect small populations

–   Ex: The Amish community carries an allele that results in short arms and legs and extra fingers and toes (1/14 vs. 1/1000)

Natural Selection

u   Still the most significant factor that causes changes in established gene pools

u   Stabilizing Selection

–   Natural selection that favors average individuals (on a normal curve) in a population

–   Reduces variation in a population

–   Ex: With spiders, larger ones are found easier and eaten and small spiders can’t find food as easily

Natural Selection

u    Directional Selection

–    Natural selection favors one of the extreme variations of a trait

–    Can lead to rapid evolution

–    Ex: The food supply in an area is limited to hard nuts. Birds with short, strong beaks will survive

u    Disruptive Selection

–    Natural selection favors individuals with either extreme of a trait’s variation

–    Can lead to evolution of 2 new species

–    Ex: A shelled, marine organism called a limpet has white, tan, and dark shells. The white and dark shells blend in on different colored rocks.  Tan gets eaten.

 

Species

u   A species is a group of organisms that look alike and can interbreed to produce fertile offspring in nature

u   Speciation is the evolution of new species

–   Occurs when members of similar populations no longer interbreed to produce fertile offspring within their natural environment

Causes of Speciation

u   95% coincide with some sort of chromosomal rearrangement

u   Physical barriers

–    Volcanic eruptions, sea-level changes, new islands forming

–    These prevent interbreeding

–    Called geographic isolation

u   Over time, may have to adapt to new types of environments

Causes of Speciation

u   Reproductive Isolation

u   Two types

–   One occurs because of geographical reasons (migrate away)

–   One occurs because of behavioral reasons

u  Some mate in fall, some in spring

Polyploidy

u   Individual with a multiple of a normal set of chromosomes

u   How does this happen?

u   New zygotes may not develop the same way as parents due to different number of chromosomes

u   May result in speciation

Gradualism

u   James Hutton & Charles Lyell

u   Theory that processes are moving at the same speed today as in the past

u   Suggests that the Earth is very old – 4.55 billion years

u   Also suggests that evolution occurs constantly, but slowly

Punctuated Equilibrium

u   Niles Eldredge and Steven J. Gould

u   Theory that speciation occurs relatively, in rapid bursts, with long periods of genetic equilibrium inbetween

u   Might occur due to drastic environmental changes resulting in quick adaptations

Divergent Evolution

u    The pattern of evolution in which species that once were similar to an ancestral species diverge, or become increasingly distinct

u    Galapagos Finches

–    Similar changes for finches that ended up on different small islands

Adaptive Radiation

u    When an ancestral species evolves into an array of species to fit a number of diverse habitats

–    a type of divergent evolution

u    Hawaiian Island honeycreepers

–    Similar in body size and shape, but different sharply in color and beak shape

–    Adapted to occupy different niches (what’s a niche)

Convergent Evolution

u    A pattern of evolution in which distantly related organisms evolve similar traits

u    Occurs when different organisms occupy similar environments

–    Adapt similar traits

u    Example:

–    Organ pipe cactus in N. and S. American vs. Euphorbiaceae in African deserts both look very similar

Review

•             Explain and illustrate why the evolution of resistance to antibiotics in bacteria is an example of directional natural selection.

•             How can geographic isolation change a population’s gene pool?

•             Why is rapid evolutionary change more likely to occur in small populations?

•             How do gradualism and punctuated equilibrium differ? How are they similar?

•             Hummingbird moths are night-flying insects whose behavior and appearance are similar to those of hummingbirds. Explain how these two organisms demonstrate convergent evolution.

•             What is divergent evolution?  How does it compare to adaptive radiation?

Quick Tour of Ch 17

u   Classification – the grouping of objects or information based on similarities

u   Taxonomy – the branch of biology that groups and names organism based on studies of their different characteristics

u   Aristotle was the first on record

–  Classified organisms into two groups: plants and animals, each with subgroups

Carolus Linnaeus

u  Introduced a system based on similar structures of organisms

u  Came up with the most commonly used classification system

u     Kingdom (humans - Animalae)

–    Animalae, Plantae, Fungi, Protista, Monera

u     Phylum (humans - Chordata)

u     Class (humans - Mammalia)

u     Order (humans - Primata)

u     Family - (humans - Homonidae)

u     Genus (humans - Homo)

u     Species (humans - sapiens)

–    Organisms in the same species can mate and produce fertile offspring

Changes to Linnaeun Taxonomy

u  Some people add a division “above” kingdom called a domain

–  Bacteria, Archaea, Eukaryota

u  Many people also use a 6 kingdom system

–    Animal, Plant, Fungus, Protist, Eubacteria, Archaebacteria

 

Binomial Nomenclature

u  All organisms have a two-word name

u  Consists of their genus and their species

–  Always italicized in type and underlined in writing

u  Genus is capitalized, species is lower case

–  Homo sapiens (human)

–  Passer domesticus (sparrow)

Classification Key

u   Sometimes called a dichotomous key

u   “Guide” for identifying different species based on observable traits

u   Useful for distinguishing between types of organisms

Modern Classification

u    Generally based on evolutionary relationships vs. physical characteristics

u    Used structural similarities, breeding behavior, geographical distribution, chromosome comparisons, biochemistry to figure out relationships

u    Cladogram (phylogenic diagram/tree) shows evolutionary history of a group of organisms

 

Cladogram for Primates

Cladogram

u    Monerans evolved first (archaebacteria probably first, then eubacteria)

–    prokaryotes

u    Protists then evolved

–    Single celled eukaryotes

–    Three general kinds of protists:  fungus like, animal like and plant like

u    Fungi, Plants and Animals evolved from the types of protists

Review

•            Why does your book use the classification system of six kingdoms instead of five?

•            What two taxa does binomial nomenclature consist of?

•            Why is classification hard to do?

•            What are the 7 Linnaean taxa?

•            How might you use taxonomic key to figure out the name of an organism?