Bio Ch 17-20

Darwin, evolution and fossils

Chapter 17

Chapter 17

What is evolution?

Organisms changing over time

What is a theory?

Well suported & testable explanation of natural phenomena

What is a population?

species subgroup who mate/reproduce together

What did Darwin observe about organisms across Galapagos Islands? (give example)

They were different everywhere. (ex: turtles: dome-shaped shell, saddleback shell, intermediate shell and finch beak sizes)

South American vs Galapagos tortoises

South America:

• eat grass, cactus fruit, flowers

Galapagos:

• No predators → larger

• eat grass → same body type

• eat cactus → modified shell, long neck

South American vs Galapagos iguana

South American:

• eat fruit

Galapagos:

• (land) eat cactus → long claws to climb

• (marine) eat algae → flat tail to swim

South American vs Galapagos finch

South American:

• eat small seeds

Galapagos:

• large seeds/small/fruit/insect → different beak sizes

What was the prevailaing belief about Earth and its organisms in the 1700s?

Fixed World View - Earth and all its forms of life have only existed and remained unchanged for a few thousand years

remove this card

remove this card

What did Darwin observe about his fossils?

• some looked like modern organisms

• others looked completely different

• many had died out

What did Darwin ask about the fossils?

• Why had so many species disappeared?

• How were they related to living species?

Who was James Hutton?

hypothesized that tectonics and erosion shaped Earth very slowly - Earth must be very old

Hutton’s influence on Darwin

If Earth is millions of years old, then organisms must have had millions of years to change

Charles Lyell

Laws of nature are constant, so whatever we see today helped shape Earth back then (volcanoes, continental drift, etc.)

Lyell’s influence on Darwin

If the Earth changes, then maybe so do organisms

Lamarck’s theory of evolution

1. Tendency towards perfection

   1. inborn urge to become more complex/perfect

   2. ex: kept trying to fly; over generations developed wings

2. Use & disuse

   1. can change size/shape of organs by using them in new ways

   2. ex: waterbirds get longer legs because they stretch them in deeper water

3. Inheritance of acquired traits

   1. organisms could pass on traits they develop

   2. ex: waterbird can pass on longer legs to children

How much of Lamarck was correct?

Correct:

• first evolution hypotheses to recognize organisms’ adaptation to environment

Incorrect:

• behavior has no effect on genes

• acquired traits aren’t heritable

Thomus Malthus (1798)

Babies are being born faster than people are dying, so if human population grows unchecked we will run out of food/living space

What did Darwin conclude about Malthus’s ideas?

struggle for existence: Since populations produce far more offspring than can survive, members of a population must compete for a finite supply of resources

Why did Darwin decide to publish his theory?

Alfred Russell Wallace sent Darwin an essay about his almost identical thoughts on evolution

Adaptation noun def

Heritable trait increasing ability to survive

3 types of adaptations

1. Anatomical (physical)

2. Physiological (body functions)

3. Behavioral

What is fitness?

Organism’s ability to survive and reproduce - survival of the fittest

In what situations does natural selection occur?

- more individuals are born than can survive (struggle for existence)

- varying fitness

3 parts of Darwin’s evolution HYPOTHESIS

1. Struggle for existence

   1. members of a population compete for finite supply

2. Survival of the fittest

   1. individuals with certain inherited variation are better adapted to environment than others

3. Common ancestry

   1. living species are descended from common ancestors, with changes over time

Struggle for existence example

Male booby with brightest blue feet “wins” female mate

Survival of fittest example

Polar bears with largest claws/teeth get most prey, and survive/reproduce the most

What is biogeography?

Study of where organisms and their ancestors lived

Evidence of evolution

• biogeography

• fossils

(also evidence for plate tectonics)

What are homologous structures?

Similar structures shared between related species, inherited from common ancestors

Vestigial organs

Organ with no useful function in an organism

Darwin’s hypothesis of how different finches came to be (what assumptions did he make?)

• common ancestors

• 1 finch arrived in Galapagos, evolving into 13

assumptions:

• must be enough heritable variation in beak shape to produce “raw material for natural selection”

• variation in beak shape must create differences in fitness

What happened when Peter & Rosemary Grant tested these Darwin’s assumptions?

• Provided concrete evidence for Darwin’s theories

• Found a great variation of heritable traits

• Individual birds with different sized beaks had different chances of survival during a drought

• Likely led to speciation

• evolution can happen quickly

Chapter 18

Chapter 18

What is a gene pool?

Consists of all genes, including different alleles, in a population

What is allele frequency/relative frequency? (how do you express it?)

Number of times an allele appears in a gene pool compared to others - a percent

doesn’t have to be expressed

3 sources of genetic variation

1. Mutation

   1. heritable change in DNA

2. Crossing over

   1. can create 8.4 million combinations from 23 chromosomes

3. Lateral gene transfer

   1. transfer of genetic material to non-offspring organism

Single vs polygenic trait

Single-gene traits:

• 1 gene

Polygenic:

• multiple genes, often 2+ genes

• many possible genotypes & phenotypes

What shape do polygenic trait graphs make, and why?

bell curves, because it’s less probable to get all extreme alleles of one type than a mix of different alleles

How does resistance (to antibiotics, pesticides, etc.) happen?

Natural selection - by chance, one can resist it, and they survive/reproduce more often

Natural selection’s impact on single gene traits

changes in allele frequencies → changes in phenotype frequency

natural selection’s 3 different kinds of impacts on polygenic traits (name them)

1. Directional selection

2. Stabilizing selection

3. Disruptive selection

directional stabilization

one end of bell curve is fittest, so bell curve shifts in that direction

ex: small & medium seeds become scarce, so large-beaked birds have the benefit

stabilizing selection

center of bell curve is fittest, so bell curve steepens

ex: human birth weight (small is unhealthy, large have trouble being born)

Disruptive selection

extreme ends of bell curve are fittest - graph dips in middle

ex: small & large seeds are abundant, so small/large beaked birds are fit

Identify kind of selection.

Dark = unfit

Light = fit

Disruptive

Identify kind of selection.

Dark = fit

Light = unfit

Directional

Identify kind of selection.

Dark = fit

Light = unfit

stabilizing

Founder effect

when a small group leaves to a new isolated location and establishes that location’s gene pool

genetic drift

allele frequencies and “evolution” change just by chance

Hardy-Weinberg principle (5 parts)

Allele frequencies will stay constant unless….

1. Nonrandom mating/sexual selection

   1. mates chosen based on aesthetics

2. Small population

   1. genetic drift doesn’t affect large populations

3. Gene flow from migration

   1. new traits may arrive or traits may migrate away

4. Mutations

5. Natural selection happens

What is speciation? (have we seen it?)

species changing so dramatically they can’t mate - haven’t seen it

Why is speciation the core theory of evolution?

remove this card

Species (singular) - how is it different from population?

species: group of organisms who CAN mate/produce offspring

population: group of organisms who DO mate

Types of isolation (name them)

1. behavioral isolation

2. geographic isolation

3. temporal isolation

behavioral isolation

two populations CAN interbreed, but WON’T because of mating rituals/behavior choices

ex: Eastern and Western meadowlark sing different courtship songs

geographical isolation

two population CAN mate, but are separated by water, mountain, etc.

ex: Abert’s and Kaibab squirrel across Grand Canyon

temporal isolation

two populations CAN mate, but mate at different times of the year

ex: orchids releasing pollen only one day

Darwin’s hypothesis of how finches speciated in Galapagos (types of isolation)

• Species A flies in from South America → Island A

• some from Species A cross to Island B (geographical isolation) - they don’t share same gene pool anymore

• each population adapts to own environment

• some from Species A cross back to Island A

• they don’t want to mate with each other (behavioral isolation)

• A and B compete for resources

• evolve in ways that increase differences, producing Species C

This repeats time and time again, now there are 13-14 species

Chapter 19

Chapter 19

What is binomial nomenclature?

genus, species (2-word naming system)

List the levels of classification

Domain Kingdom Phylum Class Order Family Genus Species

Dumb Kids Playing Catch On Freeways Get Smashed

Name all the kingdoms

Eubacteria, Archaebacteria, Protista, Fungi, Plantae, Animalia

Linnaeus’s 2-kingdom classification system

Plantae & Animalia

Name all the domains (peptidoglycan?)

Eukarya: protists, fungi, plants, animals

Bacteria: eubacteria WITH peptidoglycan

Archaea: archaebacteria WITHOUT peptidoglycan

Eubacteria: Cell type, cell structures, number of cells, and mode of nutrition

Cell type: Prokaryote

Cell structures: Cell walls with peptidoglycan

Number of cells: unicellular

Mode of nutrition: autotroph (producer) or heterotroph (consumer)

Archaebacteria: Cell type, cell structures, number of cells, and mode of nutrition

Cell type: Prokaryote

Cell structures: Cell walls without peptidoglycan

Number of cells: unicellular

Mode of nutrition: autotroph or heterotroph

Protista: Cell type, cell structures (wall? chloro?), number of cells, and mode of nutrition

Cell type: Eukaryote

Cell structures: Cell walls of cellulose, some have chroloplasts

Number of cells: most unicellular, some colonial, some multi

Mode of nutrition: autotroph or heterotroph

Fungi: Cell type, cell structures, number of cells, and mode of nutrition

Cell type: Eukaryote

Cell structures: Cell walls of chitin

Number of cells: most multicellular, some uni (yeast)

Mode of nutrition: heterotroph

Plantae: Cell type, cell structures, number of cells, and mode of nutrition

Cell type: Eukaryote

Cell structures: Cell walls of cellulose, chloroplasts

Number of cells: multicellular

Mode of nutrition: autotroph

Animalia: Cell type, cell structures, number of cells, and mode of nutrition

Cell type: Eukaryote

Cell structures: No cell walls or chloroplasts

Number of cells: multicellular

Mode of nutrition: heterotroph

Chapter 20

Chapter 20

Earth’s layers are…

Crust

Lithosphere

(asthenosphere = upper mantle)

Mantle

Outer Core

Inner Core

What are plates?

lithosphere divided into plates carrying amounts of continental/oceanic crust, float on asthenosphere

What drives plate tectonic movements?

convection currents within Earth

3 kinds of plate boundaries

1. divergent

2. convergent

3. transform

Describe divergent boundaries

• 2 plates move away from each other

• creates mid-ocean ridge volcanoes

convergent boundaries (different creations based on plate type)

• 2 plates move towards each other

• continental & continental: mountains

• continental & oceanic: volcanoes

• oceanic & oceanic: volcanic island chains

transform boundaries

• 2 plates move side-by-side

• creates earthquakes

weathering

breaking rocks chemically/physically into smaller pieces

erosion (by what medium?)

small pieces of rock are carried away by wanter, wind, or glaciers

deposition

small particles of sand, silt, or clay are carried by water where they settle out layers of sediments at the bottom

Weathering causes erosion causes deposition

know this

Igneous rocks

magma cools and hardens beneath the surface or after a volcanic eruption

Sedimentary rocks

sediments are compressed and cemented together into rocks

Metamorphic rocks

rocks change under extreme heat and pressure

How do fossils form?

• dead organisms are buried under layers of sediment → usually found in sedimentary rock and as marine creatures

• water seeps in, depositing minerals

Fossil quality varies (T/F)

true

What conditions are needed for fossil-ization?

Rapid burial in sediments immediately after death

types of fossils

• skeleton

• imprint

• amber

• eggs

• poop

Fossils are usually… complete or incomplete?

incomplete

Why will the fossil record never be complete?

We will never uncover every fossil that has formed

How does relative dating work?

• put rock layers and their fossils into a time sequence, where lowest is oldest

• use index fossils as timestamps

How does direct dating work?

• measuring radioactive decay, especially carbon-14

Describe the Miller-Urey experiments

• simulated early Earth’s conditions

• with hydrogen, methane, ammonia, & water for atmosphere and electricity as lightning

• Results: after several days, 21 amino acids were produced

• Helped show how organic compounds could have come from early Earth’s conditions

What was wrong about the Miller-Urey experiments?

They used the wrong gases to simulate early Earth

biogenesis vs abiogenesis

biogenesis: life can only come from life

abiogenesis: life can come from nonliving things

How geological, astronomical, and biological sources affected Earth’s climate

Geological: continental movements from plate tectonics created dramatic changes in temperatures

Astronomical: changes in Earth’s axis and orbit changed amount of solar radiation reaching certain parts

Biological: photosynthetic organisms took out CO₂ from atmosphere and replaced it with O₂

What percent of all species to ever live are extinct?

99%