Biology: Evolution Mechanisms

Evolution

• Definition: The process by which species change over time through the transmission of genetic information from one generation to the next.
• Mechanisms:
  • Natural Selection: The process by which individuals with favorable traits are more likely to survive and reproduce, passing those traits to their offspring.
  • Genetic Drift: The random change in the frequency of a gene or genetic trait in a population over time.
  • Mutation: A change in the DNA sequence of an individual.
  • Gene Flow: The movement of genes from one population to another, leading to genetic changes.

Genetics

• Definition: The study of heredity and variation in organisms.
• Key Concepts:
  • Genotype: The genetic makeup of an individual.
  • Phenotype: The physical and behavioral traits of an individual.
  • Dominant and Recessive alleles: Dominant alleles will be expressed if an individual has one copy of the allele, while recessive alleles will only be expressed if an individual has two copies.

Chromosomes

• Definition: Thread-like structures made up of DNA and proteins that carry genetic information in the nucleus of eukaryotic cells.
• Number of Chromosomes:
  • Humans: 23 pairs (46 total) of chromosomes.
  • Other Organisms: The number of chromosomes varies, but is typically diploid (two sets).
• Chromosomal Structure:
  • Centromere: The region where the sister chromatids are joined.
  • Telomeres: The protective caps on the ends of chromosomes.

DNA (Deoxyribonucleic Acid)

• Definition: A double-stranded molecule that contains the genetic instructions for an organism.
• Structure:
  • Double Helix: Two complementary strands twisted together.
  • Nucleotides: The building blocks of DNA, consisting of a sugar molecule, a phosphate group, and a nitrogenous base (A, C, G, or T).
• Replication: The process by which DNA is copied, ensuring that each new cell receives a complete set of genetic instructions.

Punnett Squares

• Definition: A diagram used to predict the outcomes of cross-breeding experiments, illustrating the possible genotypes and phenotypes of offspring.
• Components:
  • Parents: The two individuals being crossed.
  • Alleles: The different forms of a gene.
  • Punnett Square: A grid displaying all possible combinations of alleles from the parents.
• Predicting Offspring Traits: By analyzing the Punnett Square, we can determine the probability of different genotypes and phenotypes in the offspring.

Evolution

• Evolution is the process by which species change over time through genetic transmission.
• Natural selection favors individuals with favorable traits, increasing their survival and reproduction rates.
• Genetic drift is a random change in gene frequency in a population over time.
• Mutation is a change in an individual's DNA sequence.
• Gene flow is the movement of genes between populations, leading to genetic changes.

Genetics

• Genetics is the study of heredity and variation in organisms.
• Genotype is an individual's genetic makeup, while phenotype is their physical and behavioral traits.
• Dominant alleles are expressed with one copy, while recessive alleles require two copies.

Chromosomes

• Chromosomes are thread-like structures made up of DNA and proteins carrying genetic information in eukaryotic cells.
• Humans have 23 pairs (46 total) of chromosomes.
• Other organisms have varying numbers of chromosomes, typically diploid (two sets).
• Chromosomes have a centromere where sister chromatids join and telomeres at the ends.

DNA (Deoxyribonucleic Acid)

• DNA is a double-stranded molecule containing genetic instructions for an organism.
• DNA has a double helix structure with two complementary strands.
• Nucleotides are the building blocks of DNA, consisting of a sugar molecule, a phosphate group, and a nitrogenous base (A, C, G, or T).
• DNA replication is the process of copying DNA to ensure each new cell receives a complete set of genetic instructions.

Punnett Squares

• Punnett Squares are diagrams used to predict cross-breeding outcomes, illustrating possible genotypes and phenotypes of offspring.
• Parents, alleles, and Punnett Squares are used to determine the probability of different genotypes and phenotypes in offspring.
• Punnett Squares help predict the traits of offspring by analyzing the possible combinations of alleles from parents.