LAB:Variation in a Species What is the purpose of Part 1? (Measuring Pumpkin seeds) There is variation in size in Pumpkin plants. Variation can be measured.

LAB:Variation in a Species What is the purpose of Part 2? (Calculate how long it takes pumpkin plants to take over the Earth) There are reasons to explain why pumpkin plants have not ever taken over the Earth

LAB:Variation in a Species What is the purpose of Part 3? (Effect of predators on sweet cute Bonitos) There are reasons to explain why the population of bonitos on one island look different from bonitos on another island

What is a species? A group of living things that Are similar Can breed together in nature To produce fertile offspring.

What is a population? A group of living things that Belong to the same species Live in the same area Can reproduce together

What is a gene pool? The total collection of genes in a population at any one time.

Hardy & Weinberg What is allele frequency? 1908: Hardy and Weinberg invented the term “allele frequency” to describe the percentage of dominant and recessive alleles found in a populaton.

Hardy & Weinberg How is allele frequency measured? Example: a lizard population might have the following allele frequency for the alleles F and f: FF = 0.64(64%) Ff = 0.32(32%) ff = 0.04 (4%)

Hardy & Weinberg What is genetic equilibrium? 1908: Hardy and Weinberg invented the term “genetic equilibrium” to describe a population in which the frequency of alleles stays the same from one generation to the next.

Hardy & Weinberg How was genetic equilibrium measured? Hardy-Weinberg equations: p 2 + 2pq +q 2 = 1 p + q = 1

Hardy & Weinberg Hardy-Weinberg Equations Where p 2 is the frequency of homozygous dominant individuals Where 2pq is the frequency of heterozygous individuals Where q 2 is the frequency of homozygous recessive individuals

Hardy & Weinberg What causes genetic equilibrium? There must be……. A large population Members mating at random No mutation No migration No natural selection

Hardy & Weinberg What can cause allele frequency to change? Migration (also called gene flow) Mutation Mate selection (non-random mating) Predators, disease, famine, drought, storms, accidents.

Observing Variation (1) Variation exists in living populations. (2) Some variations are helpful and increase life span. (3) Some variations are harmful and decrease life span.

Observing Variation (4) A population may become physically separated, so two groups form. (5) As mutations and meiosis occur, new variations will appear. (6) Some offspring will survive better than others.

Observing Variation (7) Offspring that survive in one area may not survive in another area. (8) Over time, more variations will accumulate in the two populations. (9) The two populations will become different because different variations occur in the two groups.

Observing Variation (10) Individuals that die out do not get to reproduce. (12) Sometimes, a new species has formed. (11) In some cases, the two groups become so different from each other that they can no longer interbreed.

What is this Process? Evolution of species A set of natural processes that causes change in a population of living things over time.

Understanding Evolution Scientists study natural processes and look for natural explanations. I will show you as much as I can about evolution and why scientists say it is the basis of all biology. Science cannot answer every question. What if you disagree with photosynthesis?

Evolution by Natural Selection Variation exists in every population. Natural selection (predators, disease, drought, cold, famine, flood, heat…..) causes some individuals to survive while others do not. Sources of inherited variation: meiosis, crossing over, mutation. Allele frequency change is called evolution. Sometimes it causes speciation.

Jean Baptiste de Lamarck How did giraffes get long necks? Evolution by Inheritance of Acquired Characteristics

Jean Baptiste de Lamarck Animals face a need to change. Animals make themselves change Animals pass on the changes to offspring. “Inheritance of Acquired Characteristics”

Charles Darwin Age 25: set sail on 5 year voyage on HMS Beagle as “Naturalist”.

Darwin observed Charles Darwin observed animals and plants in the Caribbean, South America, the Galapagos, Hawaii, Indonesia, Africa and Europe. He took massive notes (Cornell notes?) He wrote three books about his experiences

Darwin’s Notebook

Common Ancestor

Evolution by Natural Selection Variation exists in a population. (Darwin did not know how the variation was passed…genetics was not yet understood) Some organisms survive and pass on genes…some do not. Causes of this evolution: migration, “heredity”, mate selection, predators, disease, famine, drought,

Lamarck and Darwin: How would they explain these observations? In 1960, a pesticide was sprayed at Tybee Island, GA, killing 97% of all mosquitoes. In 1979, the same pesticide killed less than 30% of all the mosquitoes. Lamarck: Wallace:

Evolution by Natural Selection Variation exists in a population. (Darwin and Wallace did not know how the variation was passed…genetics was not yet understood) Some organisms survive and pass on genes…some do not. Causes of this evolution: migration, “heredity”, mate selection, predators, disease, famine, drought,

How can evolution occur? Mutation Migration Meiosis and crossing over Genetic drift (luck) Natural Selection (predators, disease, famine, drought) Non-random mating (sexual selection)

How can allele frequency change? Mutation Migration Meiosis and crossing over Genetic drift (luck) Natural Selection (predators, disease, famine, drought) Non-random mating (sexual selection)

Evidence that evolution takes place Homologous or vestigial structures Biogeography Homologous DNA and proteins Fossil evidence Evolution observed right now

Homologous skeletal structure

Vestigial whale pelvis bones Vestigial anthers and pollen: Dandelions are asexual

Bear evolution based on homologous DNA genes

Fossil evidence of horse evolution

Whale and dolphin evolution based on DNA homology

Phylum Annelida segmented worm evolution based on fossil and DNA homology

Living examples: Phylum Annelida (segmented worms)

Evolution of flowering plants: Phlox and its relatives

Phlox evolution based on fossil and DNA homology

Evolution of Turtles, with massive fossil evidence

Biogeography

Hawaiian Monk Seals

Embryo Homology

Plant embryo homology

Common Ancestor

Homologous Structures Bees, ants and wasps have stingers which are modified ovipositors…which explains why only females can sting!

Evolution: Changes in allele frequency over time

Whale evolution

Hardy-Weinberg genetic equilibrium Allele frequency will not change as long as: The population is large, so there is no genetic drift There is no migration (gene flow) There is no mutation There is random mating There is no natural selection

The Founder Effect A few individuals are separated from the original population. All the descendants resemble the founders, even if those traits are not best for the environment. EXAMPLE: island tortoises

Genetic Bottleneck A large population declines rapidly. The survivors reproduce and the population goes up in number, but the new population resembles the survivors. The genes of the new population are often more uniform, with less variation EXAMPLE: cheetahs

Natural Selection Stabilizing selection: natural selection removes organisms at the extremes of a population….like Goldilocks.

Natural Selection Directional selection: natural selection removes organisms at one extreme and in the middle, favoring one extreme.

Natural Selection Disruptive selection: natural selection removes organisms with the average form of a trait, favoring both extremes.

How to form new SPECIES? Reproductive isolation is required. Prezygotic isolation (before fertilization) Postzygotic isolation (after fertilization the offspring is sterile)

Reproductive Isolation Allopatric speciation: GEOGRAPHY (ocean, canyon, mountain) Sympatric speciation Organisms all live in same area, isolated by song, timing, mutation

Adaptive Radiation Songbirds from South America Honeycreepers from Hawaii

Convergent Evolution

Gradualism & Punctuated Equilibrium

Why was this little sticker so controversial? Source: