Evolution Theory by Charles Darwin

Theory of Evolution

• The theory of evolution states that all organisms evolve over time through natural selection.

Evolution

• Evolution occurs when a population or species changes over time, involving changes in the gene pool.
• A population is not evolving if its gene pool remains unchanged.

Species

• A species is a group of organisms that can reproduce and produce fertile offspring.
• When a species grows apart, it can eventually become unable to produce fertile offspring due to speciation events.
• Hybrids are offspring produced by organisms that can reproduce but are infertile.

Alleles and Characteristics

• Alleles are different versions of genes that determine an individual's features and traits.
• Dominant alleles can override recessive alleles in determining characteristics.
• Polygenic alleles display one trait, while codominant alleles can express both traits.
• For example, a dominant brown eye allele can override a recessive blue eye allele, while a codominant red rose allele and white rose allele can produce a pink rose.

Mutation

• Mutation is a random change in genes during DNA replication.
• Mutation can introduce new traits and increase variation in a population by altering genes and alleles.

Differential Reproduction

• Differential reproduction is the process of evolution where certain groups in a population have more offspring than others.
• This can occur due to advantageous traits that increase an individual's likelihood of survival.

Evolution Processes

• There are five main ways populations can change:
  • Shrinking of population, which reduces genetic variation
  • Mutation, which introduces new alleles
  • Mating, which can favor certain groups over others
  • Gene flow, which brings in new genetic material
  • Adaptation and natural selection, which favor certain alleles over others

Speciation and Reproductive Isolation

• Speciation is the process of a species dividing into multiple species over time.
• Reproductive isolation occurs when a species is unable to interbreed with other species.

Overproduction and Competition

• Overproduction occurs when more individuals are conceived than the environment can sustain.
• Competition is the consequence of overproduction, where groups must compete for resources.
• Advantageous traits are more likely to be passed down due to competition.

Inherited Variation

• Inherited variation occurs due to sexual reproduction, where alleles are randomly passed down from parents to offspring.
• This leads to genetic variation across individuals in a species.
• Sexual reproduction allows for mutation, which increases variation in a population.