natural

2.  “Survival of the Fittest”
 Selection for traits that are most successful in current environment
 A constant process – environments change and therefore so do
factors that determine success

3.  Darwin proposed that
organisms descend from
common ancestors and change
with time, diverging from the
original common form
 This causes the evolution of
new species

4. 1. Overpopulation
2. Competition
3. Variation
4. Survival of the Fittest
5. New Species

5.  Organisms tend to produce
many offspring – more than
the environment can support
 Organisms will reproduce
until something stops them
(usually food)

6. • Because of overpopulation, individuals compete with one another over
limited resources  food, water, shelter, mates
• Competition occurs both within and between species

7. • Individuals of a population vary in their traits and characteristics
• This variation is passed on to offspring.

8. • Individuals with
advantageous genetic
traits are better adapted
to their environment
• This increases their
chance of survival
• This is called survival of
the fittest

9.  New species results by
inheritance of trait(s), on
genes, that give them another
advantage over others
 New species evolve!

10.  Where one species evolves into one or more other species
 Also called ADAPTIVE RADIATION

11.  An inheritable characteristic that provides an advantage for
survival and reproduction.
 Adaptations can be:
1. Structural – a part the organism has to help it survive
 Ex: Speed, camouflage, claws, quills, etc.
2. Physiological – a metabolic or chemical adaptation to help it survive
 Ex: ability to maintain internal temperature; use less water for photosynthesis; produce a
poisen
3. Behavioral – something the organism does to help it survive
 Ex: Migration; solitary vs. herds; flying in formation

12. 1. Darwin’s finches
2. Peppered moth
3. Antibiotic resistant
bacteria
4. Pesticide resistant
mosquitoes
**Do not copy!

13.  Alleles exist with a certain frequency in populations of organisms
 The available genes and alleles in a population are called the “gene pool”

14.  Changes in the structure of genes introduce new alleles to populations and disrupt
equilibrium
 Not all mutations are good, many are fatal
 This is the source of all new alleles

15.  Preference for a particular allele will increase its frequency in a population over
generations
 Selection can happen in three different ways

16. 1. If the environment favours the average of the distribution, the selection is
called stabilizing selection

17. 2. If the environment
favours one extreme, the
selection is directional

18. 3. If the environment favours both extremes, the selection is disruptive

19.  Mutations: The Science of Survival
 https://www.youtube.com/watch?v=qVmusHZtQms (Darwin & Natural Selection)
 20:00 to 29:29 (part 3?)