Bio 11- Adaptations and Evolution & Evidence for evolution

Adaptation

A characteristic that helps an organism survive and reproduce in its environment

Includes structures and behaviours for finding food, a mate, for protection, and for moving from place to place

(ex. bears hibernating)

Adaptations for a snake

Can unhinge jaw

Can smell with tongue

Adaptations for a kangaroo

Large ears to hear predators

Powerful back legs to hop long distances

Adaptations for a spider

Can easily sense vibrations on the ground

Special hairs to tickle predators

Adaptations for a monkey

Apposable thumbs

Teeth for omnivorous diet

Adaptations for a cheetah

Camouflage from spots

Adaptations for an Elephant

Trunk used to bathe, drink, and wash themselves

Large tusks for defence

Natural Selection

Process where organisms better adapted to their environment tend to survive and produce more offspring, leading to evolutionary change.

These are organisms that have traits that highly benefit them to have a greater likelihood of survival and higher rate of reproduction success

4 Key Conditions for Natural Selection to occur

• struggle for survival

• inheritable variation within a population

• variation of fitness amongst members of the same population

• lots of time

Origin of Species Hypothesis I

Aristole believed that all plants and animals had been placed on Earth from the start and never changed

This is incorrect

Origin of Species Hypothesis II

Life has changed over time

This branches out into Lamark’s theory and Darwin’s theory

Lamark’s theory of Evolution

i) “Law of Use and Disuse”

ii) “Inheritance of Acquired Characterstics”

Law of Use and Disuse

The more a body part is used, the more developed it will be

(ex. an ancestral giraffes stretches its neck a lot, so the neck will become longer over time)

(ex. penguins never used wings, so wings became smaller over time)

Inheritance of Acquired Characteristics

The more developed traits are passed down to its offspring

(ex. never used thumbs, their offspring would have weak thumbs)

Disproving Lamark’s Theory

August Weissman cut the tails off 20 generations of parent mice

If Lamark was correct, the tails of the 20th generation should be underdeveloped because tails were not used

Result of August Weissman Experiment

No change in tail length or size, therefore disproving Lamark

Darwin’s Theory of Evolution

His theory is that evolution happens by natural selection

He proposes that organisms with advantageous traits are more likely to survive and reproduce, passing on those traits to their offspring.

Struggle for survival

Competition between organisms to survive in the same environment

Occurs when there are more animals born than the environment can handle because there isn’t enough food and resources

Result of Struggle for Survival

Not all animals survive

Inheritable Variation within a population

Within a population, organisms have differences like longer giraffe necks due to variations in the gene responsible for neck length

Inheritable Trait

A trait that can be passed down to offspring

Traits caused by variations in the genes (DNA) can be passed down onto the offspring

Variation of fitness amongst members of the same population

An organism must stay alive to reproduce

When they reproduce, they will get good genes that result in a useful trait

(ex. having a longer neck only matters if it helps the organism survive long enough to reproduce and pass on those genes)

Fitness

Determined by the organism’s ability to produce offspring

More offspring = higher

Lots of Time

Natural selection causes a gradual change that happens over many generations, this is a must for the result of all the organisms acquiring the advantageous traits

(ex. long neck in all giraffes)

Evolution

A process of gradual change that takes place over many generations

During which organisms slowly change some of their physical and behavioural characteristics

Speciation

The product of evolution

Formation of new, distinct (different) species due to evolution

Distinct species

Two organisms when they produce infertile offspring

Two organisms produce a hybrid animal offspring

Fertile Offspring

The offspring of two organisms of the same species

3 type of evolution

• convergent

• divergent

• coevolution

Define Convergent Evolution

Two or more species share similar traits that did not come from a common ancestor

Convergent evolution, why?

Happens because when different species that live in similar environments, they will develop similar characteristics that allow better survival in the given environment

(ex. to survive better in the water, sharks, and dolphins developed fins)

Analogous Structures

Shared structures between organisms that have the same function, but come from a different origin

(ex. wings of bats, birds, and insects)

Define Divergent Evolution

Two or more species diverge from a common ancestor

The species will look very different from each other despite sharing the same ancestors

Divergent evolution, why?

Happens when part of a population becomes isolated due to migration or geographical barriers

Organisms of the divided population, will become adapted to different environmental changes, making them different

(ex. humans, bats, frogs, porpoises, and horses have the same limbs as us humans as we inherited from a common ancestor)

Define Coevolution

Happens when two or more species influence each other’s evolution because of their interactions

Coevolution, why? (ex.1)

In order for it to happen, the species must have dependence on each other, and reciprocal influence

Example: Butterflies and Birds

1) The bird wants to eat the mimics because the monarchs are inedible, so it evolves to be able to differentiate them better

2) The mimic itself evolves more to look like the inedible monarch

3) The monarch evolves to look less like the mimic

Artificial selection

Also called, selective breeding

Happens when humans, rather than the environment, decide which traits are useful

(Ex. Cauliflower, broccoli)

Advantages of selective breeding

It tries to establish certain traits that animals will pass to the next generation

Examples of desirable traits in selective breeding

Disease resistance, calmness, more lean meat, endurance

Disadvantages of selective breeding

Results in decreased genetic diversity found in the population

Undesirable traits from both parents may appear in the offspring

(Ex. Diseases and health problems that accumulate in the population)

Homologous structures

Parts of the body that are similar in structure (same origin but have different functions)

This occurs because of Divergent evolution

(Ex. The relationship between human, cat, and whale)

Vestigial structures

A structure that has been reduced in size and function but may once have been complete and functional

(Ex. Whale’s leg bones)

The more recent two species are separated = more

More closely related they are

Gradualism

Means that changes happen slowly and gradually over a long period of time rather than suddenly or in large leaps

Punctuated equilibrium

Punctuated equilibrium suggests that species often experience long period of little or no significant change, stopped by short periods of rapid and substantial change

Factors that cause punctuated equilibrium

• Mass extinction events

• Migration into new environments

• Isolation of small populations