Evolution

=Dum dum dum=

= Evolution! =

Charles Darwin spent about 22 years collecting different species of animals, and studying them. Wallace is much younger and one day having malaria in Southeast Asia, it suddenly struck him about how animals can evolve. So when Wallace wrote to Charles Darwin to explain his theory, Dar

Observations of Charles Darwin:

1. populations have potential to increase exponentially 2. Populations are fairly constant in size 3. Natural resources are limited 4. There is variation within a species, and variation is inherited

Deduction 1: Only some organisms survive. There is a struggle for existence(due to limit of natural resources) among individuals in a population. This keeps the population at a certain size.

Deduction 2: Individuals with favourable variations are more likely to survive and reproduce. The total no. of gene pool of these individuals are more likely to increase--as the no. of gene pool increase, it evolves to new species. So accumulation of variation over many generations is evolution.

NATURAL SELECTION.
For example:

There's a pair of birds, that produce a large number of offsprings...in some of these offsprings, there are lighter coloured ones. These lighter coloured ones will be easily caught by predator. Hence over time, only dark coloured birds survive, and pass their gene pool to their offsprings...so more and more birds become dark coloured till eventually, they are all dark coloured! These birds adapted to their situation and changes some of their physical characteristics.

Natural selection is an incredibly method to generate evolution.
1. **Genetic variation**-- 2. **Overproduction of offspring**--there are too many offsprings that can actually survive 3. **Struggle for existence**--In any population, the excess production of individuals results in competition for foods, and space even mates. (hummingbirds compare fiercely for nectar) Natural selection results in change in wing shape, allow hummingbirds to fly faster, change the length and shape of bills etc. Slight change in bill length can affect their survival.

Note: A hummingbird cannot change its traits over its lifetime--it is in their DNA. Traits seen must be found in genes and hence be able to be passed on to the next generation. Traits are not by intent. Note: Change always happens in a population. Note: Natural selection occurs over a long period of time results in evolution. As long as the environment changes, a population will continue to evolve--e.g. changes in natural resources for life

In different environments, hummingbirds have different traits: to adapt to the different flowers in the environment.

4. **Differential survival and reproduction**: will determine the composition of gene pool, where traits will be more suited to survive in the environment. Some traits survive better--favourable individuals with advantageous traits: frequency of the gene will increase in the gene pool

In hummingbirds, many of their species are very young--only evolved in the past 2-3 million years. Small changes over generations, and these changes build up over time.

Genetic variation is heritable: not based on "needs" or "intents".
 * Environmental pressures ** change with time, habitat, etc. Variation in a population is caused by meiosis, mutation, cross fertilization, environmental influences, etc. Over production of off springs--> where organisms produce more young than needed.

Global warming: May affect the change in species, and these changes accumulate over time and shape the change that happen in a population.

In theory of evolution: As long as you're not the last one, your genes may not be passed on. They don't necessarily die. Qn: Then if they don't die, how do their gene pool decrease? They will still reproduce. =/

VARIATION + DIFFERENTIAL REPRODUCTION + HEREDITY = NATURAL SELECTION

Difference between Larmarck and Darwin Newly acquired traits somehow get passed down to offspring ; those with traits which kelp survival will tend to survive and have offspring who inherit their traits

Stabilizing Selection: Both sides of the smaller population with not advantageous traits are "eliminated" : end up with a stablized range. Directional Selection: One type is allowed to survive better over another category. Population will be shift to one side--directional. Disruptive or Diversifying Selection ====Because of Global Warming, mosquitoes are found in ALASKA! ====

** Adaptation & Fitness **
-Any HERITABLE trait that suits an organism to its function in its niche -It may be STRUCTURAL, PHYSIOLOGICAL(heart rate, metabolism) or BEHAVIORAL: For example, huddling behavior to keep warm. Bears know that when it's cold they will hibernate. -Genetive adaptation has to be FUNCTIONAL in the organism's natural habitat

-It is not ACCLIMATIZATION which is an organism's ability to adapt DURING ITS LIFETIME to changing environmental conditions Adaptation actually refers to a population

Examples: Higher surface area to volume ratio allows foxes to lose heat in deserts; lower surface

Fitness is a measure of how well-suited an organism is to survive in its habitat and its ability to maimize numbers of offspring to reproductive age Components of fitness:
 * Survival
 * Fecundity : How many offsprings you can produce
 * Mating success

Industrial Melanism: Natural selection pressures due to manmade influences have led to color changes in certain species; When it changes, it changes the population of species; In Industrialization, the soot covers the tree trunks, causing tree trunks to be black--moths that are darker coloured survive better than those who have the colour of the tree trunks. However, in places where there are less industrialization, the moths with colour of the tree trunks camoflauge and survive better.

Antibiotic resistance: Evolution matters now because it is constantly changing. Type of tuberculosis does not respond to the medication they have. They have to eat a variety of medication is to kill ALL of them. If they don't, the bacteria that isn't completely killed will continue multiplying and become resistant to ALL drugs.