W h a t i s E v o l u t i o n ?. EVOLUTION: . the process of change over time idea that new species develop from earlier species by accumulated changes “descent with modification”. Evolution is NOT…. It is NOT a fact ...it's a theory :
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It is NOT a fact...it's a theory:
1. “Acquired Characteristics”: Through use and/or non-use, features needed for survival are developed in each individual
2. Inheritance:“acquired characteristics”
passed on to offspring, who can continue that development.
3. New Species: enough differences have developed that new species arrise.
2. “Survival of the fittest” (not necessarily the strongest): more adaptive traits = more survival; more offspring
1.Environment changes thus creating a “need” to change.
1.Variations of inheritable
features which already normally exist.
2. Development of new features,
“in order to survive.” or “so that
one can survive.”
2.Environment “screens out”
(or SELECTS) features contributing
to survival, and tends to eliminate
3. Those with traits which help survive and have more offspring, who inherit those traits.
3.Newly acquired traits somehow
get passed down to offspring.
4.New species form,
4.New species form,
1.Organisms produce more offspring than can survive.
2.There is variation among offspring.
3.There are limited resources
(not enough food, water, space,
etc. for everyone).
4.The organisms best fit to their environment will survive and the others will not.
aka. Adaptive Radiation
Radius and ulna
Not a lot of teeth
Big salivary glands
offspring, the offspring
is not fertile.
The biological species concept is based on viable offspring, rather than physical similarity.
Modes of Speciation
1. Allopatric speciation
- geographically separate ranges; gene flow interrupted and new species evolve
2. Sympatric speciation
- geographically overlapping populations; chromosomal changes and nonrandom mating reduce gene flow.
Remember: Species arise when individuals in a population become isolated one from the other.
Polar Bear and Grizzly Bears territories are overlapping (due to global warming) causing these 2 species to mate and produce offspring who can reproduce.
1. Habitat isolation - Two species live in the same area, but occupy different habitats; rarely encounter each other.
2. Behavioral isolation - Signals that attract mates are often unique to a species. (e.g., different species of fireflies flash different patterns)
3. Temporal isolation
- Two species breed at different times of the day or during different seasons.
5. Gametic isolation
- Gametes must recognize each other.
(Example: fertilization of fish eggs, chemical signals between sperm and egg allows sperm to “recognize” the correct egg)
Why is genetic variation important?
Extinction happens: 99% of all species extinct