EVOLUTION

 CHAPTER 11: WE ARE IN CONSTANT EVOLUTION

Charles Darwin proposed that species can change over time, that new species come from pre-existing species, and that all species share a common ancestor.

CHARLES DARWIN AND ALFRED RUSSELL WALLACE

Charles Darwin and Alfred Russell Wallace were scientists who spent time exploring the natural world on expeditions to the tropics. They observed species that were similar but had distinct differences. Wallace and Darwin both observed similar patterns in other organisms and independently conceived a mechanism to explain how and why such changes could take place. Finally, Darwin called this mechanism natural selection, which is the process whereby organisms better adapted to their environment tend to survive and produce more offspring (the babies or children of animals and people).

DO NOT FORGET THIS CONCEPTS!!

VARIATION

Natural selection can only take place if there is variation, or differences, among individuals in a population. Genetic diversity in a population comes from two main sources: mutation and sexual reproduction.

MUTATION

A mutation can have one of three outcomes for the organism's appearance (or phenotype):

1. A mutation may affect the phenotype of the organism in a way that gives it reduced fitness-lower likelihood of survival, resulting in fewer offspring

2. A mutation may produce a phenotype with a beneficial effect on fitness

3. Many mutations, called neutral mutations, will have no effect on fitness.

ADAPTATION

It is a heritable trait that aids the survival and reproduction of an organism. Adaptation can also be defined as a change over time that helps us survive. Adaptation to an environment comes about when a change in the range of genetic variation occurs over time that increases or maintains the match of the population with its environment

TYPES OF EVOLUTION

We have two different types of evolution: Divergent evolution (when two species evolve in different directions from a common point) and Convergent evolution (when similar structures arise through evolution independently in different species).

The four basic causes of evolution are: natural selection, mutation, genetic drift and gene flow.

You can also define two types of evolution:

Microevolution = Gradual change of a population through time, generation to generation. You can see this happening in real time. Ex: insects in a tree that can camouflage will survive better than others that can’t, so they will have better evolution.

Macroevolution = Processes that give rise to new species and higher taxonomic groups with widely divergent characteristics.

The evidence for evolution is:

• Fossils show gradual changes through time

• Can determine age and categorize them all over the world to determine when organisms lived relative to each other

• Successive fossils show evolution of teeth shapes and foot and leg anatomy

ANALOGOUS vs HOMOLOGOUS STRUCTURES

Analogous structures: similar in function and appearance, but do not share an origin with a common ancestor. Ex: the wings of a dolphin, penguin, shark…

Homologous structures: structures share similarities because of a common ancestor.

HARDY-WEINBERG EQUILIBRIUM

The Hardy-Weinberg Equilibrium is an important fundamental principle of population genetics, which states that “genotype frequencies in a population remain constant between generations in the absence of disturbance by outside factors”.

This fundamental principle works with the following assumptions: No natural selection, no mutation, no migration, large populations and random mating.

COMMON MISCONCEPTIONS ABOUT EVOLUTION

• Evolution is just a theory

• Individuals evolve

• Evolution explains the origin of life

• Organisms evolve on purpose

• Evolution is controversial among scientists

• Other theories should be taught

REFERENCES

(n.d.). What is Darwin's Theory of Evolution? LIVESCIENCE. Retrieved November 3, 2023, from https://www.livescience.com/474-controversy-evolution-works.html

(n.d.). What is evolution? Study.com. Retrieved November 3, 2023, from https://study.com/academy/lesson/forms-patterns-of-evolutionary-change.html

(n.d.). Patterns of evolution. Sparknotes. Retrieved November 3, 2023, from https://www.sparknotes.com/biology/evolution/patternsofevolution/section1/