EVOLUTION

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EVOLUTION

Evolution is the change in the characteristics of a species over many generations.

Theories about evolution

Lamarckism

By studying the anatomy of different species, he suggested that species change over time in response to changes in the environment. He believed that organisms tend to become more complex over time as they develop more acquired characters. However, other scientists pointed out examples that did not fit the theory, such as acquired characteristics cannot be passed on.

Darwinism

Charles Darwin developed a new theory of evolution, organisms are capable of multiplying very rapidly through reproduction, but that population are limited by the amount of food and space available, predators and diseases. So, individual organisms need to complete with other individuals to survive. The ones that are best adapted to their environment are most likely to survive and reproduce. When organisms reproduce, they pass on their characteristics to the next generation, so the most useful characteristics are more likely to be passed on (over many generations, this leads to a gradual evolution).

Darwin studied how farmers breed plants and animals with useful or desirable characteristics. He called this process artificial selection. He contrasted this with natural selection, when wild plants and animals pass on beneficial characteristics.

VOYAGE OF THE BEAGLE

Darwin visited many remote islands and coast to prove his theories.

· Galapagos Islands: Most of the lands animals were endemic to the islands. Each island was inhabited by different species of the same genuses.

EVIDENCE FOR EVOLUTION

Is believed that all life from Earth has gradually evolved from a common ancestor.

Fossils

Show that the organism that lived on Earth in the past were different from the ones alive today. The order in which the fossil appear supports are that the classes of vertebrates evolved in an order (fish,amphibian,reptiles and then mammals). Some fossils show intermediate stages of evolution (platypus/ornitorrinco).

Anatomy

· Homologous features: species who share complex physical features that may have inherited from a common ancestor. · Analogous features: animals that have changed their color to camouflage. · Vestigial structure: when an organism do not use a certain part of the body so it disappears.

Biogeography

The geographic distribution of species can be explained by evolution together with the movement of tectonic plates.

Genetic Analysis

All living things hace DNA with the same genetic code that produces the same 20 amino acids. Genetic sequencing shows that species with similar physical characteristics usually have more similarities in their genomes that species that look very different from each other.

Direct Observation

Evolution generally occurs very slowly, so it is impossible to observe it directly. However, some species adapt very rapidly, so we can see evolution to pesticides.