Day 3 & 4) Evolution - Life Science 11 - Joanna Peng

Adaptation

A characteristic that helps an organism survive and reproduce in its environment. They include STRUCTURES and BEHAVIORS for finding food, a mate, for protection, and for moving from place to place.

Ex. A polar bear’s thick fur is an adaptation that helps it live in cold places.

Adaptation of snakes (give 1 example)

1) They can expand their jaw to swallow their prey whole.

2) They can smell with their tongue.

Adaptation of kangaroos (give 1 example)

1) They have large ears to hear predators.

2) They have a pouch for carrying young until they’re able to survive on their own

Adaptation of spiders (give 1 example)

1) They can easily sense vibration on the ground.

Adaptation of monkeys (give 1 example)

1) They have opposable thumbs to help them grasp items and climb trees more safely

Adaptation of leopard (give 1 example)

1) They have spots that camouflage them from predators and prey alike

Adaptation of elephants (give 1 example)

1) They use their trunk to bathe, drink and wash themselves

Natural Selection

It’s a phenomenon occurring in the natural world where organisms possessing traits that are highly suited to their environment have a greater likelihood of survival and a higher rate of reproductive success.

The four key conditions necessary for Natural Selection to occur are:

1) Struggle for survival/Competition between organisms to survive

2) Inheritable Variation

3) Variation of Fitness

4) Lots of time

Aristotle’s theory: Scala Naturae (“ladder of nature”)

Aristotle believed all organisms had been placed on Earth at its existing form, and nothing has ever changed.

Lamarck’s theory of evolution (Lamarckism)

Part 1) “Law of Use and Disuse” means the more you use a body piece, the more developed it will become.

Part 2) “Inheritance of Acquired Characteristics” means the more developed or underdeveloped traits are passed onto their offspring

Disproving Lamarck’s theory (August Weismann challenged the theory)

August Weismann cut off tails of 20 generations of mice and there were NO CHANGES, which proves Lamarck’s theory wrong. If Lamarck was correct, the offsprings of the mices should have small, underdeveloped tails.

Darwin’s theory of evolution

Darwin’s theory explains that evolution happens because of natural selection. Meaning, organisms with helpful inherited traits are more likely to survive and reproduce, so those traits become more common over many generations. Natural selection does not mean organisms choose to change.

For example, some ancestors were born with shorter legs or longer, more flexible bodies. Those body shapes helped them move through grass, sand, tunnels, or tight spaces. They survived better and passed on those genes. Over many generations, legs became smaller and eventually disappeared.

Struggle for survival/competition between organisms to survive

There are more animals born than the environment can handle because there isn’t enough food and resources. As a result, not all animals can survive.

Inheritable variation (within a population)

Inheritable variation means differences between living things that can be passed from parents to offspring through genes. Inheritable variation helps evolution happen because some helpful traits can be passed to the next generation.

Variation of fitness

Fitness means how well an organism survives and it is determined by an organism’s ability to produce offspring. The greater the number of offspring an organism can produce, the higher its fitness level.

1) an organism must stay alive to have offspring

2) when it has offspring, it will give them its good genes that result in a useful trait

Lots of time

Over many generations, natural selection causes gradual changes in the population, resulting in all organisms acquiring the advantageous trait.

There could still be big changes reproduction of bacteria: they reproduce every 20 minutes!

(Our biology 11 class’s magic number is 100 years)

Evolution

A process of gradual change that takes place over many generations during which organisms slowly change some of their physical and behavioral characteristics.

Speciation

Formation of a new distinct/different species due to evolution. 2 organisms are considered distinct species when they produce an infertile offspring; Oppositely, 2 organisms of the same species would produce fertile offspring.

For example, Ligers are male lion and female tiger mating in captivity. Therefore, Ligers cannot reproduce and they aren’t a species; they’re known as hybrid animals

Name 3 types of evolution

1) Convergent

2) Divergent

3) Coevolution

Convergent Evolution

Convergent evolution means different species evolve similar traits because they live in similar environments.

Ex. To survive in water, sharks (fish) and dolphins (mammals) developed fins

These shared structures are called analogous structure

Analogous structure

Analogous structures are body parts in different species that have a similar function, but they evolved separately and do not come from the same recent ancestor structure.

Ex. A bird, bat, and an insect each developed wings to survive in the air, but their wings are all developed very differently.

Divergent Evolution

Divergent evolution means closely related species/species with a common ancestor become more different over time because they adapt to different environments. This happens when a population gets split apart/isolated, and the separated groups slowly evolve differently.

Ex. Humans, frogs, bats, porpoises, and horses have the same bones in our limbs because we inherited this structure from a common ancestor.

The splitting up often happens when there’s geographic isolation (meaning part of a population becomes separated by distance or a physical barrier).

Coevolution

Coevolution means two species evolve together because they affect each other’s survival.

Ex. Predator and prey, flowers and bees, etc.

Ex. A plant may evolve chemical defenses, and an insect may evolve resistance to those chemicals; This “race” continues for generations.