Natural selection theory

Natural selection theory

Charles Darwin and Alfred Wallace

What traits does it have that help it to survive?

Gregor Mendel

Where did the polar bear get its traits from?

Evolution

Charles Darwin

Alfred Wallace

Where did the polar bear get its traits from?

Charles Darwin

Alfred Wallace

Why aren't the polar bear and the grizzly bear the same?

How does biodiversity arise?

Natural Selection is a theory that tries to answer that question.

Natural selection theory

The theory of Natural Selection (NS) is credited to both Darwin and Wallace.

Charles Darwin

Alfred Wallace

Natural selection is a creative process where organisms develop new traits over generations. These traits persist in their environment, and this creates diversity over time.

two perspectives of natural selection

creative perspective

eliminative perspective

Natural selection

eliminative perspective

This perspective focuses on how organisms That are not well-suited to new conditions die. it explains survival, but not biodiversity.

key aspects about natural selection theory (eliminative perspective)

1. Environmental conditions determine which organisms can survive.

key aspects about natural selection theory (eliminative perspective)

2. Organisms that survive are able to reproduce and pass on their traits to their offspring.

key aspects about natural selection theory (eliminative perspective)

3. Variation within a species is crucial for survival. Without variation, an entire population is at risk of dying out of conditions change.

4. Changes in environmental conditions can pressure organisms to either adapt and survive or face extinction.

Natural selection: Eliminative perspective

Natural selection (eliminative perspective)

Answer:1. Which animal is most likely to go extinct? Why? 2. Which animal is most likely to survive and reproduce (adapt) in the degraded jungle environment and why?

Degraded jungle environment

Depict the animals you think could survive in this degraded jungle:

Jungle environment

Write the animals that you can observe in the jungle environment:

key aspects about natural selection theory (eliminative perspective)

Environmental conditions determine which organisms can survive.

1. environmental conditions

Organisms that survive are able to reproduce and pass on their traits to their offspring.

2. inheritance of traits

Variation within a species is crucial for survival.

3. variation

4. Changes in the environment

Pressure organisms to either adapt and survive or face extinction.

Reflecting on the eliminative perspective of Natural Selection

but where do new traits come from?

does eliminating explain diversity... or only explain extinction?

Why are so many species on earth?

two perspectives of natural selection

creative perspective

eliminative perspective

natural selection theory (creative perspective)

The creative perspective focuses on how new traits appear and persist.

key aspects about natural selection theory (creative perspective)

1. New traits arise from variation.2. The environment does not kill; helps to shape.

key aspects about natural selection theory (creative perspective)

3. Diversity appears because new traits are kept over generations.

key aspects about natural selection theory (creative perspective)

3. Diversity appears because new traits are kept over generations.

key aspects about natural selection theory (creative perspective)

3. Diversity appears because new traits are kept over generations.

key aspects about natural selection theory (creative perspective)

4. When the environment changes the variations allow the organisms to adapt (survive and reproduce).

eliminative and creative perspectivescomparison

Activity: try to explain(Example)

The climate becomes colder

Creative perspective:

Some variations are able to live in that colder climate. New traits appear to persist in this new environment.

eliminative perspective:

Animals without enough fur will die.

try to explain

A new type of food appears in the ecosystem

The climate becomes very rainy

A group of organisms become isolated on an island

Creative perspective: eliminative perspective:

Creative perspective: eliminative perspective:

Creative perspective: eliminative perspective:

summary

environment

variation

Influences the creation and persistance of new traits or the elimination of some traits that are not adaptive.

Is the diversity of traits within species. It is important for persistance as it allows populations to adapt to changing environments.

summary

adaptation

it's not the strongest

extinction

A heritable trait that improves an organism's ability to persist and reproduce in its specific environment.

The adaptations take a lot of time. Thousands or millions of years. When the environment change so fast, there is no time to adapt.

It's about the most well-adapted to a specific environment.

Relationships and common ancestry

Natural selection theory was difficult to accept.

Indohyus

changes over time

The changes are slow. They depend on the environment and what organisms need to persist and reproduce.

In fact, all living organisms share a common ancestor: LUCA (Last Universal Common Ancestor)

Environmental Changes Throughout Earth’s History