Natural vs Artificial Selection

Evolution

The change in inherited traits in a population/species from one generation to the next.

Natural Selection

States that those individuals who are better adapted to their current environment will survive better and therefore pass on these traits to the next generation.

Evolution by Natural Selection

Natural selection makes a population better adapted to the environment over time and

The organisms best adapted to the environment will survive the best, produce more offspring and have these traits passed down to the next generationmakes harmful traits appear less frequently.

Over long periods of time, differential reproduction will change the overall genetic composition of the population to better suit the changing environment

Differential Reproduction

The fitter individuals reproduce more than the less fit

Darwin’s Finches

During his 1835 visit to the Galapagos Islands, Charles Darwin observed finches with diverse beak shapes, which led him to propose that these birds, now known as "Darwin's finches," evolved from a common ancestor through natural selection, adapting to different food sources

Lamarck’s Theory of Evolution

Jean-Baptiste Lamarck, 1809

Stated that Changes Are Adaptations To environment acquired in an organism’s lifetime

Said acquired changes were passed to offspring

Lamark’s Law of Use and Disuse

If a body part was used, it got stronger

If body part NOT used, it deteriorated

Proven incorrect

Natural Selection

Results when the characteristics of a population of organisms change over many generations

Happens because individuals with inherited traits survive specific environmental conditions and pass on their alleles to their offspring

Requirement: MUST be diversity within a species

• Wouldn’t be antibiotic resistance if all bacteria were the same

Selective Pressure

Environmental Factors– select for certain characteristics, and against others

• Abiotic: Non-living, Natural disasters

• Biotic: Living, predators, parasites, competition for resources

Environment exerts a selective pressure on a population

Natural Selection is Situational

Natural selection does NOT anticipate changes in environment – there is no purpose or direction

Individuals in a population have varying traits by chance

• One trait may happen to fit the situation and be more likely to survive

Fitness: the relative contribution an individual makes to the next generation

Artificial Selection

Humans select for certain traits, whereas in natural selection, environmental conditions decide which population will survive

Biotechnology

The use of technology and organisms to produce useful products

Selective breeding

a form of artificial selection

Problems with Selective Breeding – Undesirable Traits

Hip Dysplasia in dogs

Purebreds are more prone to this disease than cross-breeds

Inbreeding encourages negative traits- the gene pool is less diverse

Hip dysplasia is common in: Saint Bernard, Great Danes, Labs, German Shepherds, etc.

Monocultures

Extensive plantings of the same varieties of a species over large expanses of land

Advantage: Easier to manage and take care of fields

Herbicides, insecticides and fertilizers are manufactured to meet the needs of a specific crop species

Risks: If a new disease or insect infests the crop population, the whole population could be killed or severely damaged

Gene Banks

Established to protect against monoculture disasters

Contain populations of ancestors of modern plants with various genetic combinations that allowed them to reproduce Seeds can survive for long periods of time, so they can be recovered from early settlements

This genetic diversity is then available to introduce to modern plants if needed