Biology: Reproduction and Cell Division

Reproduction

• Asexual reproduction requires only one parent, while sexual reproduction requires two parents.
• Offspring produced via asexual reproduction are genetically identical to their parents.
• Offspring produced by sexual reproduction are genetically unique, with a mix of traits from both parents.

Types of Asexual Reproduction

• Budding: a new individual grows from a parent cell, eventually separating from the parent.
• Fragmentation: a parent cell breaks into multiple fragments, each developing into a new individual.
• Binary fission: a parent cell divides into two identical daughter cells.

Types of Sexual Reproduction

• Internal fertilization: fertilization occurs within an organism's body, e.g., in humans.
• External fertilization: fertilization occurs outside an organism's body, e.g., in fish.

Mitosis

• Steps of mitosis:
  • Interphase: cell growth and DNA replication.
  • Prophase: chromatin condenses, and the nuclear envelope breaks down.
  • Metaphase: chromosomes align at the center of the cell.
  • Anaphase: sister chromatids separate.
  • Telophase: nuclear envelope reforms, and chromosomes uncoil.
  • Cytokinesis: cytoplasm divides, and cell splits.
• Mitosis produces two identical daughter cells, each with the same number and type of chromosomes as the parent cell.

Cancer

• Cancer occurs when cell division becomes uncontrolled, leading to abnormal cell growth and tumor formation.

Male and Female Reproductive Systems

• The purpose of the male reproductive system is to produce sperm cells.
• The male sex cell is a sperm cell.
• The purpose of the female reproductive system is to produce egg cells.
• The female sex cell is an egg cell.

Fertilization

• Fertilization occurs when a sperm cell fuses with an egg cell, resulting in a zygote.

Variation of Traits

• Chromosome: a thread-like structure carrying genetic information.
• Diploid cell (2n): a cell with two sets of chromosomes, one from each parent.
• Haploid cell (n): a cell with one set of chromosomes, e.g., a gamete.
• Gamete: a reproductive cell, e.g., sperm or egg cell.

Meiosis

• Purpose of meiosis: to produce gametes with unique genetic combinations.
• Process of meiosis:
  • Meiosis I: reduction division, resulting in two haploid cells.
  • Meiosis II: equational division, resulting in four haploid gametes.
• In females, meiosis produces one egg cell and three polar bodies.
• In males, meiosis produces four sperm cells.

Crossing Over and Genetic Variation

• Crossing over: the exchange of genetic material between homologous chromosomes during meiosis.
• Genetic variation: the difference in genetic traits between individuals, resulting from meiosis and crossing over.

Mutations

• Types of mutations:
  • Gene mutations: changes in a single gene.
  • Chromosomal mutations: changes in chromosome structure or number.

Genetics (Mendelian & Non-Mendelian)

• Trait: a characteristic or feature of an organism.
• Gene: a unit of heredity carrying genetic information.
• Allele: a variant of a gene.
• Homozygous: an individual with two copies of the same allele.
• Heterozygous: an individual with two different alleles.
• Dominant: an allele that masks the effect of another allele.
• Recessive: an allele that is masked by a dominant allele.
• Genotype: an individual's genetic makeup.
• Phenotype: an individual's physical and behavioral traits.

Non-Mendelian Traits

• Codominance: when both alleles of a gene have an equal effect on the phenotype.
• Incomplete dominance: when one allele does not completely mask the effect of another allele.
• Sex-linked traits: traits carried on sex chromosomes.

Punnett Squares and Pedigrees

• Punnett squares: diagrams used to predict the probability of offspring genotypes and phenotypes.
• Pedigrees: diagrams used to track the inheritance of traits in a family.

Evidence for Evolution

• Relative dating: determining the age of a fossil or rock layer relative to others.
• Stratification: the layering of rock formations, with older layers at the bottom.
• Homologous structures: similar structures in different organisms, e.g., forelimbs.
• Analogous structures: similar structures in different organisms, with different functions.
• Vestigial structures: structures that have lost their original function.
• Convergent evolution: the development of similar traits in different organisms.
• Divergent evolution: the development of different traits in different organisms.

Evolution and Natural Selection

• Charles Darwin: credited with developing the theory of evolution.
• Heritable trait: a characteristic that can be passed from parent to offspring.
• Fitness: an organism's ability to survive and reproduce.
• Adaptation: a trait that enhances an organism's fitness.
• Natural selection: the process by which better-adapted organisms are more likely to survive and reproduce.
• Speciation: the formation of new species from a single ancestral species.

Classification and Biodiversity

• Binomial nomenclature: the system of naming species using a genus and species name.
• Taxonomic levels: domain, kingdom, phylum, class, order, family, genus, species.
• Cladogram: a diagram used to show the relationships between organisms.
• Cladogram reading: organisms that share a common ancestor are grouped together.