Life Science Study Guide: Reproduction and Genetics

Sexual reproduction

Produces an offspring when genetic materials from two different sex cells combine.

Egg

The female sex cell that forms in an ovary.

Sperm

The male sex cell that forms in a testis.

Fertilization

The process where an egg cell and a sperm cell join together.

Zygote

The new cell that forms after fertilization.

Diploid Cells

Cells that have pairs of chromosomes.

Body cells

Diploid cells that make up the organism.

Homologous chromosomes

Pairs of chromosomes that have genes for the same traits arranged in the same order.

Haploid Cells

Cells that have only one chromosome from each pair of chromosomes.

Meiosis

A process where one diploid cell divides to make four haploid cells.

Meiosis I

The first division in meiosis where each pair of duplicated homologous chromosomes separates.

Meiosis II

The second division in meiosis where sister chromatids separate to produce four haploid cells.

Importance of meiosis

Forms sex cells with the correct haploid number of chromosomes, maintaining the correct diploid number when sex cells join.

Genetic variation

Created by meiosis, resulting in slight differences among individuals that might be advantageous in changing environments.

Mitosis

A process where a body cell and its nucleus divide once to produce two identical cells.

Asexual reproduction

A process where one parent organism produces offspring without meiosis and fertilization.

Fission

Cell division in prokaryotes where DNA is copied and the cell splits to form two identical offspring.

Mitotic cell division

A type of asexual reproduction where an organism forms two offspring through mitosis and cell division.

Budding

A type of asexual reproduction where a new organism grows on the body of its parent by mitosis and cell division.

Advantages of Sexual Reproduction

Produces offspring with a new combination of DNA, resulting in genetic variation.

Disadvantages of Sexual Reproduction

Organisms must mature to produce sex cells and searching for a mate takes time and energy, exposing them to risks.

Budding

A process where a new organism grows on the body of its parent by mitosis and cell division.

Regeneration

Occurs when an offspring grows from a piece of its parent.

Examples of Regeneration

Sea stars, sea urchins, sea cucumbers, and planarians can reproduce through regeneration.

Regeneration of Body Parts

Many animals can regenerate damaged or lost body parts; this is not reproduction as new individuals are not produced.

Vegetative Reproduction

A form of asexual reproduction in which offspring grow from a part of a parent plant.

Cloning

A type of asexual reproduction developed by scientists that produces identical individuals from a cell or cluster of cells taken from a multicellular organism.

Tissue Culture

A cloning method where plant growers use a meristem to make a copy of a plant with desirable traits.

Genetic Copy

A clone is a genetic copy of its parent because all of its chromosomes come from one parent.

Asexual Reproduction

Enables organisms to reproduce without a mate.

Rapid Offspring Production

Asexual reproduction enables some organisms to rapidly produce a large number of offspring.

Genetic Identity in Asexual Reproduction

Asexual reproduction produces offspring that are genetically identical to each other and to their parent, resulting in little genetic variation within a population.

Heredity

The passing of traits from parents to offspring.

Gregor Mendel

An Austrian monk who performed experiments in the 1850s that helped answer questions about how traits are inherited.

Genetics

The study of how traits pass from parents to offspring.

Pea Plants in Genetics

Ideal for genetic studies because they reproduce quickly, have easily observed traits, and allow control over reproduction.

True-Breeding Plant

A plant that, when self-pollinated, always produces offspring with traits that match the parent.

Cross-Pollination

Mendel's method of selecting which plants pollinated other plants.

Hybrid Plants

The first-generation purple-flowering plants produced from crosses between true-breeding plants with purple and white flowers.

Mendel's 3:1 Ratio

Mendel noted a 3:1 ratio in his experiments, where purple flowers grew from hybrid crosses three times more often than white flowers.

Dominant Factor

A genetic factor that blocks another genetic factor.

Recessive Factor

A genetic factor that is blocked by the presence of a dominant factor.

Second Generation Plants

In Mendel's experiments, about 75 percent had purple flowers (at least one dominant factor) and 25 percent had white flowers (two recessive factors).

Self-Pollination vs Cross-Pollination

Self-pollination occurs when a plant fertilizes itself, while cross-pollination involves fertilization between different plants.

Self-pollination

Occurs when pollen from one plant lands on the pistil of a flower on the same plant.

Cross-pollination

Occurs when pollen from one plant reaches the pistil of a flower on a different plant.

Chromosomes

Threadlike structures inside each cell's nucleus that contain genetic information.

Mendel's factors

Parts of chromosomes that determine traits, with each offspring containing chromosomes from both parents.

Gene

A section on a chromosome that has genetic information for one trait.

Alleles

Different forms of a gene.

Phenotype

How a trait appears or is expressed.

Genotype

The two alleles that control the phenotype of a trait.

Dominant alleles

Represented by uppercase letters in genetics.

Recessive alleles

Represented by lowercase letters in genetics.

Homozygous

When two alleles of a gene are the same.

Heterozygous

When two alleles of a gene are different.

Ratio

A representation of chance outcomes, such as 50:50 or 1:1.

Punnett square

A model used to predict possible genotypes and phenotypes of offspring.

Pedigree

A diagram that shows phenotypes of genetically related family members and clues about their genotypes.

Incomplete dominance

When the offspring's phenotype is a blend of the parents' phenotypes.

Codominance

When both alleles can be observed in a phenotype.

Multiple alleles

Genes that have more than two alleles.

ABO blood type

A trait determined by multiple alleles.

Polygenic inheritance

Occurs when multiple genes determine the phenotype of a trait.

Human eye color

An example of polygenic inheritance.

Environmental factors

Non-genetic influences that can affect phenotypes.

Hydrangea flower color

Determined by the soil in which the hydrangea grows.

Acidic soil

Produces blue flowers in hydrangeas.

Basic (alkaline) soil

Produces pink flowers in hydrangeas.

Naturalist

A person who studies plants and animals by observing them.

Darwin's theory of evolution

The theory best supported by evidence today regarding the evolution of species.

Variations

Slight differences among members of the same species.

Limiting resource

A resource, such as food, that is in short supply and causes competition among members of a species.

Natural selection

The process by which populations of organisms with variations that help them survive in their environments live longer, compete better, and reproduce more than populations that do not have the variations.

Adaptation

A characteristic of a species that enables the species to survive in its environment.

Structural adaptations

Adaptations that involve shape, size, color, and other physical features.

Behavioral adaptations

Adaptations that involve the way organisms act.

Functional adaptations

Adaptations that involve internal body systems that affect organisms' biochemistry.

Camouflage

A structural adaptation that aids members of a species in blending in with their environment.

Mimicry

An adaptation in which one species resembles another species.

Artificial selection

The breeding of organisms for desired characteristics, as caused by humans.

Selective breeding

The process of breeding organisms for specific traits.

Vertebrate

An animal with a backbone.

Invertebrate

An animal that does not have a backbone.

Collagen

A protein that surrounds animal cells and helps them keep their shape.

Eukaryotic

Organisms whose cells contain a nucleus and other organelles enclosed within membranes.

Multicellular

Organisms that consist of more than one cell.

Energy for life processes

Energy that animals obtain by eating other organisms.

Digest food

The process by which animals break down food to absorb nutrients.

Animal Classification

The grouping of animals into categories based on shared characteristics.

Animal kingdom

The broad classification that includes all animals, with about 95 percent being invertebrates.

Species extinction

The process by which a species ceases to exist due to inability to adapt to environmental changes.

Evolution

The process by which species develop adaptations over time to survive in changing environments.

Galápagos tortoises

A species of tortoise that exemplifies natural selection through variations that help them compete for food.

Biochemistry

The study of chemical processes within and relating to living organisms.

Species variations

Differences among individuals of the same species that can affect survival and reproduction.

Environment changes

Alterations in the living and nonliving parts of an ecosystem that can impact species survival.

Symmetry

Describes an organism's body plan.

Radial symmetry

An animal can be divided into two parts that are nearly mirror images of each other anywhere through the central axis.

Bilateral symmetry

An animal can be divided into two parts that are nearly mirror images of each other.