EVOLUTIONEVOLUTION

It is a two step process:It is a two step process:

1. The production of variation in a populationNew phenotypes defined by new genotypes

2. Non-random aspects of survival and reproduction The furless rabbits cannot survive in the cold English weather

Natural selectionNatural selection

Natural Selection is a two step processNatural Selection is a two step process Step One: The Production of VariationStep One: The Production of Variation

•Mutations: Modification of the DNA sequence, New genes/alleles appear in the genome

New recipes or modification of the original recipesWatch HAIKU video

• Meiosis: Cell division that takes place in the reproductive organs and that produces gametes.

Gametes are specific cells that contain ½ of the genetic information, ½ of the chromosomes

- recombination due to chromosomes crossing-over one another- random movement of chromosomes during division

• Random mate selection & fertilization

Natural Selection is a two step processNatural Selection is a two step process

Step Two: Non-random aspects of survival and reproductionStep Two: Non-random aspects of survival and reproduction

•Superior success of certain phenotypes

•Nonrandom mate choice (SEXUAL SELECTION – Slideshow on Haiku)

Lemurs of Madagascar

Amazonian Frogs

Bred Pigeons came from a single original species

Humans select traits for dogs, pigeons and other animals when they breed them.

Who selects the traits for wild plants & animals?

INDIVIDUALS THAT HAVE TRAITS THAT ARE BEST ADAPTED FOR THE CURRENT ENVIRONMENT ARE THE ONES THAT SURVIVE TO BREED AND PASS ON THEIR

GENES TO THE NEXT GENERATION.

NOBODY!!

Remember the furless rabbits in England: Organisms not possessing the beneficial traits either die or don’t have as many offspring.After a few generation, the “unfit” allele becomes rare and can even disappear from the population’s gene pool.

There is no agent involved in natural selection.

Natural selection is a process of elimination

Natural Selection is Survival of the fittest in a specific environment

What acts as a selection pressure on a What acts as a selection pressure on a population?population?

• Competition for food

• Competition for a mate

• Changes in the environment

• Predators

• Parasites/diseases

Directional Selection: Mimicry Directional Selection: Mimicry (mimic the environment)(mimic the environment)

Examples of selection pressures...Examples of selection pressures...• PredatorsPredators - variants with adaptations allowing them to escape

predators have more offspring- e.g. speed, defensive weapons, camouflage, mimicry

• Prey/FoodPrey/Food - variants with adaptations allowing them to obtain food have more offspring

- e.g. Speed, senses for finding prey/food, weapons for killing prey or obtaining food, camouflage for stealth

• ClimateClimate - those who can survive new climate best have more kids

- e.g. ice age, change in climate due to migration.

• MatesMates - variants with adaptations allowing them to attract a mate to have offspring

- e.g. strong, attractive, good provider

Example #1: Escaping PredationExample #1: Escaping PredationPeppered MothPeppered Moth• Early trees had light-colored bark• Only the light-colored moths survived.

Selection was for less melanin.• After industrialization, the tree bark was

darker.• Only the darker colored moths now survived.

Selection was for more melanin.

Example #2: Obtaining FoodExample #2: Obtaining Food• The neck of the Giraffe• Co-evolution with

Acacia Trees• Selection pressure is

source of food

Example #3Example #3• The leaf bug• The selection pressure is

predators• It’s strategy is to mimic a

leaf

Camouflage, Mimicry & DecoysCamouflage, Mimicry & DecoysPurposePurpose - escape from predators, sneaking up on prey

CamouflageCamouflage - favors individuals who most resemble environment

Mimicry Mimicry - favor individuals who most resemble something harmful, unappetizing, or non-threatening

DecoysDecoys - favor individuals who use lures or decoys to attract other animals to be eaten or help them unwittingly

Other Mimicry Examples Other Mimicry Examples

1. Viceroy and Monarch butterflies (predators)

2. Walking stick (predators)

3. Crab with rock garden on shell (food/predators)

4. Cobra mimic (predators)

5. Angler Fish with lure (food)

6. Orchid and wasp (fertilization)

• The coloring so closely resembles that of the female wasp Colpa aurea that males of the species are attracted to the flower and pick up pollen during their attempts at copulation.

• The orchid also produces pheromones to attract male wasps.

The labellum of Ophrys speculum Orchid.

Example #4: Increases fertilizationExample #4: Increases fertilization