Evolution by Natural Selection

Chapters 14-18

Charles Darwin, DOB 1809, On the Origin of Species by Means of Natural Selection, HMS Beagle – 1831-36

Greeks – life arose in water and more complex followed simpler ones

Later Aristole said life was fixed (ps. he’s wrong)

Judeo-Christians agreed Mid 1700s fossils of “strange animals” were

found Jean Baptiste de Lamark suggested

acquired traits were inherited. Used = got better, Unused = go away. (ps…he’s half wrong)

History

Dad wanted him to get into medicine, then he went to become a priest – Met John Henslow – took a cruise.

While on the boat he read Principles of Geology by Charles Lyell. ◦ “mountains rise cm by cm” ◦ The way the rain falls today is the same way it fell

1billion years ago.

◦UNIFORMITARIANISM Learned about Thomas Malthus

◦ Human population should be huge but - War, Disease, Famine limits the population

History

So Darwin is on a cruise…◦ Finds sea animal fossils thousands of feet above sea

level◦ Finds FINCHES similar to the mainland but 600miles

out to sea GALAPAGOS ISLANDS ◦ Realizes that kids look like parents

After his trip, he thinks about this stuff for a little while…like 20years

Alfred Wallace sends him a paper that is the same idea that he has come to and Darwin quickly publishes. The conclusion…?

History

Organisms that exist today are modified versions of older organisms.

The environment chooses the organisms that are best fit to reproduce (natural selection).◦ The better fit the organism the more babies it will

produce, the more of those genes are in the gene pool.

◦ Traits that help an organism survive better and make more babies are ADAPTATIONS

Descent with Modification

1. Fossils 2. Biogeography 3.Homologous/Analogous Structures 4. Embryology 5. Molecular Biology (macromolecules) 6. Vestigial Structures

Evidence – 6 pieces

Traces of long dead organisms Sediments Law of superposition:

◦ Which happened first, tree falling or it snowed? Fossil Record:

The theoretical ‘stack’ of all fossils, in order

1. Fossils

Align and fix the locations in place. Answer the following questions:

1. Which locality is the oldest? How do you know?2. Which locality is the youngest? Where might you

find this in the Earth’s crust?3. Approximately how many years are represented

in your localities? Are there any huge gaps?4. Why aren’t all the fossils in the same place?5. Is there a pattern to the complexity of the fossils?6. How do fossils form? What does this tell you

about the organisms that we find as fossils (or what about the one’s we don’t find)?

7. Do you think fossils are strong evidence for evolution? Why or why not.

Fossil Lab

Organisms that are relatively close (NJ and PA) are more alike than organisms that are far apart.◦ More pouched animals in Austrailia◦ Galapagos Finches

2. Biogeography

‘Homo’ means … so these are parts in different species of animals that are the same.

Analogous – same function but different structure

3.Homologous/Analogous Structures

Figure 13.11

In the early stages of development, many species are similar.

4. Embryology

Large compounds in organisms are sometimes similar◦ Protein◦ Hemoglobin◦ Starch

5. Molecular Biology (macromolecules)

Remnants of structures that served a purpose in ancestral organisms but have little or no function now.◦ Appendix◦ Wisdom teeth◦ Tails

6. Vestigial Structures

The organism that is best fit to the environment makes the most babies and passes on the most genes.

DEPENDS COMPLETELY ON GENETIC MAKEUP◦ Individual variation (longer legs, sharper teeth,

darker color) If its not the environment choosing but

people we call it ARTIFICIAL SELECTION◦ Cows◦ Sheep◦ Bacteria◦ Chemicals - ddt

Natural Selection

Gene pool – all of the genes in a population Population – a group of mating individuals in

the same place at the same time. We can identify if evolution is taking place

based on the Hardy-Weinburg Equation◦ p2 + 2pq + q2 = 1

Certain events can cause evolution to occur more quickly◦ Bottle neck event◦ Founder event◦ Gene flow – immigration, emmigration◦ Mutation

Figure 13.22

Figure 13.23

Sometimes evolution occurs in a specific pattern◦ Directional Selection◦ Disruptive Selection◦ Stabilizing Selection

Names and groups organisms according to their characteristics and evolutionary history

Carolus Linnaeus (1707-1778) Binomial Nomenclature

◦ Species identifier Varieties- peach and nectarine Subspecies – different area

A species is defined as organisms that can reproduce and form fertile offspring.

Taxonomy

Systematics – classification in the context of evolution◦ Fossil record◦ Morphology◦ Phylogenic tree

Cladistics – derived characters◦ Cladograms◦ Weird relationships

Systematics vs Cladistics

Domains – ◦ Eukarya◦ Bacteria◦ Archaea

Kingdom◦ Phylum

Class Order

Family Genus

Species

Animalia Plantea Fungi Protista Eubacteria Acheabacteria

Kingdoms (Modern Bio p348-9)

What is living?◦ Order◦ Regulation/Homeostasis◦ Growth and Development◦ Energy Utilization◦ Respond to the environment◦ Reproduction◦ Evolution

Spontaneous Generation- living things from nonliving things (frogs came from mud)

Francesco REDI 1650: Disproved spontaneous generation with meat, flies, jars

Lazzaro SPALLANZANI 1750: Disproved spontaneous generation with boiled broth, new story-vital force

Louis PASTEUR 1850: Disproved both spontaneous generation and vital force with s-shaped flask

Story of Life

Miller and Urey Experiment on how life began◦ Water + ammonia + ◦ CO2 + Nitrogen =◦ Organic compounds!◦ PROKARYOTES

Endosymbiosis- Lynn Margulis 1950

◦ One or a few microorgs◦ Living together became◦ our organelles =◦ EUKARYOTES

Story of Life

Found everywhere Kingdoms Bacteria, Archaea Mostly unicellular and very small No nucleus or organelles Shapes: Bacilli, cocci, spirochete Photoauto/heterotroph- Chemoauto/hetero-

how they eat Pathogen

Prokaryotes

Lynn Margulis- endosymbiont theory◦ Smaller prokary climbed inside larger prokay and

was happy together Kingdoms Protista, Plant, Fungi, Animals Larger cells, have nucleus and organelles VERY diverse

Eukaryotes