Natural Selection Survival of the fittest Haha More

Natural Selection “Survival of the fittest”

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More examples of Evolution x 1 l x 2 l

UNIT 3 Chapter 7: Introducing Evolution Birds are a diverse group of animals. Traits from beak to colour to nutrition are adapted to the environment in which they live and reproduce.

UNIT 3 Chapter 7: Introducing Evolution Section 7. 1 Adaptation and Variation • Extinct species have disappeared from Earth completely, and all species face this possibility • What factors explain how and why some species survive and some do not? – diversity of the organisms within a species – behaviour – interactions with the environment (A) Camouflage allows this stick insect (Eurycnema goliath) to blend in with its environment and avoid being eaten by predators. (B) Many owls such as this barn owl (Tyto alba) can sneak up on their prey because of another adaptation: fluffy feathers make their flight quite silent.

UNIT 3 Chapter 7: Introducing Evolution Section 7. 1 • Adaptations of structure, behaviour, or a physiological process give some organisms a better chance of survival than those without the adaptations *within a species • This survival advantage allows those organisms to reproduce and pass on their adaptations

Let’s take a look at some adaptations that have “stuck” Related species of insects called mantids have diverse shapes and colors that evolved in different environments.

Rabbits? l Animals brought from Europe changed in body size, weight and ear size as they adapted to the hot, dry Australian climate

Honeycreepers l As its favourite source of nectar began disappearing, the Scarlet honeycreeper (Hawaii) sought nectar elsewhere and its bill became sharper

Snails? l Marine snails (New England) changed its shell shape so that it became thicker, likely in response to being hunted by crabs

Polar Bears l How are they able to survive through the harsh winters in the Arctic?

Venus Fly Trap l Plants have adapted to become carnivorous!

UNIT 3 Chapter 7: Introducing Evolution Section 7. 1 Adaptations and Survival Adaptations occur after long periods of time – Why? • Adaptations (changes) are the result of random, heritable mutations in DNA that accumulate over generations • Help an organism survive and reproduce What determines if a change will stay in the population/species? • interaction with the environment determines whether a mutation is positive or negative for the individual organism

UNIT 3 Chapter 7: Introducing Evolution • • The variations within a species are the structural, functional, or physiological differences between individuals As a variation becomes more common, it will be passed on to more offspring • Eventually, it will be considered a trait in the population Section 7. 1

UNIT 3 Chapter 7: Introducing Evolution Section 7. 1 Mimicry • A type of structural adaptation where a harmless species physically resemble a harmful species – why? – Predators avoid the harmless species as much as they do the harmful one Organisms with the structural adaptation of mimicry, such as the viceroy butterfly (top), have coloration or structures that are similar to harmful or bad-tasting species, such as the monarch butterfly (bottom).

UNIT 3 Chapter 7: Introducing Evolution Section 7. 1 The English Peppered Moth: From Variation to Adaptation The English peppered moth (Biston betularia) is an excellent example of how the proportions of some inherited characteristics in a population change in response to changes in the environment. Those changes are viewed as evolutionary adaptations. The peppered moth has three colour variations: • greyish-white with black dots • black • intermediate colour between the above

Natural Selection in Action

UNIT 3 Chapter 7: Introducing Evolution Section 7. 1 Observations Around 1848, the black variety made up 2% of the peppered moth population in Manchester, England. During the next 50 years, Manchester became the site of intense industrial development. By 1898, 95% of the moths were black. However, the rural areas had a lower frequency of black moths. What could explain these trends?

UNIT 3 Chapter 7: Introducing Evolution Section 7. 1 Explanation • Before the Industrial Revolution, the bark on many trees in Manchester was covered with light-coloured lichen • During the Industrial Revolution, soot pollution from factories killed the lichen and blackened the bark • At first, greyish-white moths were camouflaged; later, black moths were camouflaged [camouflage = protection from predators] • The moths that were camouflaged lived longer, were able to reproduce, and produced more offspring with the same coloration.

UNIT 3 Chapter 7: Introducing Evolution Section 7. 1 Conclusion The ratio of greyish-white-to-black moths in the population changed over successive generations due to an environmental change. In the 1950 s, England enacted clean-air legislation. How might the environment have changed after the 1950 s? Predict what happened to the peppered moth population.

Natural Selection l Darwin put it best: l l “Individuals having any advantage, however slight, over others, would have the best chance of surviving and procreating their kind” This notion did not come to Darwin at lightning speed! Like a good scientist, his theory came from several observations and inferences

Darwin’s Observations l Observation #1: Individuals within a species vary in many ways

Individuals of a Species Vary

Darwin’s Observations l Observation #2: Some of this variability can be inherited

Darwin’s Observations l Observation #3: Every generation produces far more offspring than can survive and pass on their variations

Darwin’s Observations l Observation #4: Populations of species tend to remain stable in size

Darwin’s Inferences l Inference #1: Members of the same species compete with each other for survival

Darwin’s Inferences l Inference #2: Individuals with more favourable variations are more likely to survive and pass them on. Survival is not random.

Darwin’s Inferences l Inference #3: As these individuals contribute proportionately more offspring to succeeding generations, the favourable variations will become more common (i. e. natural selection)

Darwin in 3 Points Natural selection is differential success in reproduction (unequal ability of individuals to survive and reproduce) l Natural selection occurs through an interaction between the environment and the variability inherent among the individual organisms making up a population l The product of natural selection is the adaptation of populations of organisms to their environment l

How did Darwin do it? l Darwin was able to formulate his theory without: fossil evidence, l the ability to date rocks, l or any knowledge/understanding of the genetic basis of inheritance and variation! l l What is the source of variation?

• This evolutionary tree of the elephant family is based on evidence from fossils

Artificial Selection l l l Breeding animals and plants for desirable characteristics Mass production of ‘ideal’ organisms artificially removes unwanted traits Examples: dogs, horses, oil and corn

Antibiotic Resistance: Evolution by Natural Selection l l Occurs by bacteria with specific traits that allow them to survive exposure to drugs and therefore thrive, re-ignite infections, and launch to new hosts Two innate characteristics allow bacteria to evolve that ‘quickly’: l Fast doubling time l Ability to swap genes with other bacteria

A demonstration….

Homework l Clover Case Study