Biology Term 3 Study cards

Genetic variation

Differences in DNA among individuals within a population that arise from mutations, gene flow, and sexual reproduction.

Environmental variation

Differences among individuals in a population caused by environmental factors rather than genetic differences.

Ways genetic variation is produced

1. Mutations - random changes in the DNA sequence. 2. Gene flow - exchange of genes between populations through migration.

Gene vs. Allele vs. Chromosome

A gene is a segment of DNA that codes for a protein, an allele is a variant form of a gene, and a chromosome is a structure made of DNA and proteins that carries genes.

Inherited vs. Acquired characteristics

Inherited characteristics are traits passed from parents to offspring through genes, whereas acquired characteristics are traits gained during an individual's life due to environmental influences.

Sexual reproduction and genetic variation

Sexual reproduction increases genetic variation by combining genetic material from two parents, leading to offspring with unique combinations of alleles.

Four things needed for natural selection

1. Variation in traits among individuals. 2. Differential reproduction - some individuals are more successful at surviving and reproducing. 3. Heritability - traits must be passed down to offspring. 4. Overproduction of offspring.

Natural selection and species adaptation

Natural selection allows species to adapt over time by increasing the frequency of favorable traits that enhance survival and reproduction.

Organisms with helpful traits and survival

Organisms with helpful traits are more likely to survive and reproduce because they can better cope with environmental challenges, leading to increased reproductive success.

Insect resistance to insecticides

Insects can become resistant to insecticides through natural selection when those with mutations allowing resistance survive and reproduce, passing those beneficial traits to their offspring.

Allele frequency

The proportion of a specific allele among all allele copies in a population.

Natural selection changing allele frequencies

Natural selection can change allele frequencies over time by favoring alleles that contribute to traits increasing survival and reproduction, thereby increasing their frequency in the population.

Helpful alleles and commonality

A helpful allele becomes more common over generations because individuals with that allele tend to survive and reproduce more successfully, passing it on.

Harmful alleles and commonality

Harmful alleles can become less common over time because individuals carrying them may have lower reproductive success and thus contribute fewer offspring to future generations.

Environmental changes and allele frequencies

Changes in the environment can affect allele frequencies by altering which traits are advantageous, leading to changes in survival and reproduction rates of individuals with certain alleles.

Antibiotic resistance in bacteria

Antibiotic resistance in bacteria is an example of natural selection because bacteria with mutations conferring resistance survive antibiotic treatment and reproduce, passing resistance traits to their offspring.

Selective breeding vs. natural selection

Selective breeding involves humans choosing specific traits to breed for, while natural selection is a natural process where environmental pressures determine which traits are favorable.

Natural selection and pest resistance

Natural selection has caused some insects to become resistant to pesticides as individuals with mutations allowing resistance survive pesticide applications and pass this trait on.

Natural selection in conservation

One example is the breeding of endangered species to enhance genetic diversity and increase the survival rate of their populations through natural selection.

Camouflage and natural selection

Camouflage enhances survival rates by allowing organisms to blend into their environment, making them less visible to predators, resulting in those traits being favored by natural selection.

Natural selection and bird beak size

Natural selection could lead to larger beaks in birds if larger beaks provide an advantage in accessing food resources, leading those with the trait to survive and reproduce more successfully.