What is a species

1
What is a species?

• A species is a group of organisms that are so
  similar that they can interbreed (make offspring
  together).
• Examples?

2
What is MICROEVOLUTION?

• Microevolution
• how often a gene (ex. A gene for drug
  resistance) shows up in a population of organisms
• - Evolution that happens on a small scale (within
  a single population, ex. bacteria, weeds,
  mosquitos)
• Examples
• Pests have acquired genes to resist pesticides
• Weeds

Genes
Herbicide resistance
GERMS
Genes
Antibiotic resistance
3
What is a gene pool?

• A gene pool is the COMBINED genetic info.
• Of all the members of a particular population
• (ex. Homo sapiens, canis familiaris)
• Because all members of a given species
• Interbreed they share a common group of
• genes! (name some?)

Humans share some genes with dogs But dont have
all genes in common!
DOGS AND HUMANS IN 2 DIFF. GENE POOLS!!!
4
Genetic Drift

• Is a random change in the number of times a
  particular gene appears.
• A blonde and a redheaded person have kids
• 7 of 8 have blonde hair. This could not have been
  predicted but is a chance occurrence
• Result More blonde hair genes in that family and
  chances are they will have blonde haired kids.

5
What is Macroevolution?

• Large-scale evolutionary changes that occur over
  a long period of time

6
Macroevolution caused this
7
Geographic Isolation

• Form of reproductive isolation in which 2
  populations are separated physically by
• geographic barriers such as rivers, mountains,
  or stretches of water.
• Result A species can be split into 2 or more
  different populations
• SPECIATION When a new species is formed.

8
Geographic Isolation did thisWhy?
9
What is Directional selection?P. 398

• This is a form of evolution/natural selection
• This is a BELL CURVE

Upper end of curve
Lower end Of curve
Upper end of curve
Most individuals
Less
Less
(SHAPED LIKE A BELL)
10
Directional Selection(continued)

• A type of NATURAL SELECTION that especially
  applies to individuals at the upper part/end of
  the bell curve
• They have a higher fitness so their numbers will
  increase and bell curve will shift toward right.

11
Directional Selection Graph
12
What is Stabilizing Selection?P. 399

• -Individuals near the center of curve have higher
  fitness than those at either end
• Example Range of baby weights
• Lowest wt. 6 lbs 2 oz.
• Highest wt 9 lbs 2 oz
• Lower baby wgtshigher mortality (death)
• Higher baby wgts diff.delivery by mom
• Ideal wgt. 7 lbs 7 oz
• Evolution result Middle wgt babies are most
  common among humans

13
Graph-Stabilizing Selection
7 lbs 7 oz
6 lbs 2 oz
9 lbs 2 oz
14
Disruptive Selection

• -When individuals are upper and lower end of
  curve have the best chance of survival
• Example
• Suppose Pop of birds Medium seeds
• 
  disappear
• Large/Small
  seeds
• become more
  
• common

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Result Birds with Large or Small Beaks survive
Med. Beaks die off
Graph of Disrup. Selection