Asexual Reproduction Overview

Asexual Reproduction

• Definition: Formation of offspring without a mate
• Characteristics: Creates identical offspring (clones)
• Methods:
  • Binary Fission/Mitosis: DNA replication, cell elongation, division into two daughter cells. (Bacteria, protists, ameobas)
  • Budding: Parent produces a small bud that detaches or stays to form a colony. (Hydra, yeast, some coral)
  • Spores: Parent produces many spores (like seeds). (Molds, fungi, some ferns)
  • Fragmentation: Fragment of the organism breaks off and forms a new individual. (Starfish, flatworms, some plants - like pothos, spider plants)
  • Vegetative Reproduction/Propagation: Plant reproduction not involving seeds. (Strawberries, runners, grafting, tubers, suckers, aspen trees, tulips/daffodils)
• Advantages:
  • Large numbers of offspring
  • No mate needed
  • Little/no parental care
  • Only one organism needed
• Disadvantages:
  • Offspring are clones (vulnerable to disease)
  • Vulnerable to extreme temperatures
  • Competition for resources (food, space)

Sexual Reproduction

• Definition: Reproduction by combining male and female reproductive cells (gametes)
• Characteristics: Genetically diverse offspring produced by two parents
• Advantages: Genetic variation, allowing survival in changing environments
• Disadvantages:
  • Time-consuming (finding a mate, fusion of gametes)
  • Exposure to risks (disease, predators, harsh environments) while finding a mate
  • Fewer offspring
  • Slower maturation for offspring
  • May need parental care

Meiosis

• Definition: Cell division producing gametes (sex cells)
• Goal: Create four haploid daughter cells (half the genetic material) – genetically different
• Stages:
  • Meiosis I:
    • Prophase I: Chromosomes condense, nuclear membrane disappears, homologous chromosomes pair up and cross over
    • Metaphase I: Homologous pairs line up in the middle
    • Anaphase I: Spindle fibers contract, separating homologous chromosomes to opposite poles
    • Telophase I and Cytokinesis: Nuclear membrane reforms, two haploid cells are formed
  • Meiosis II: Similar stages to Mitosis, resulting in four haploid daughter cells, each with unique genetic combinations
• Haploid: Half the genetic material (n)
• Diploid: Double the genetic material (2n)
• Human Haploid Number: 23
• Human Diploid Number: 46

Fertilization

• Definition: Fusion of male and female gametes' nuclei to form a zygote (a single cell)
• Process (humans):
  • Sperm meets egg in the fallopian tube
  • Sperm head reacts with the egg membrane
  • Cell membranes fuse; sperm nucleus enters egg
  • Egg membrane hardens to prevent further sperm entry
  • Egg and sperm nuclei combine to form a diploid zygote

Heredity, Traits, and Genes

• Heredity: Passing of biological traits/characteristics from parents to offspring through inheritance of genes.
• Traits: Genetically determined characteristics (physical or behavioral).
• Genes: Segment of DNA on a chromosome; basic unit of heredity, determining traits.
• Offspring: New living things that come from one or more parents.

Nature vs Nurture

• Nature: Genetic traits inherited from parents.
• Nurture: Environmental influences that shape a person throughout life.
• Together: Both nature and nurture contribute to the development of an individual.

Darwin's Finches and Evolution

• Darwin's Theory: Variations in sexual reproduction (sometimes caused by mutations) with favorable traits are passed on. This leads to the development of new species.
• Finches: Finches on different Galapagos Islands evolved variations in beak shapes and sizes depending on the available food sources. This demonstrates the principle of natural selection in evolution.

Gametes

• Definition: Sex cells (sperm and egg) containing half the number of chromosomes in a normal body cell (haploid).
• Male Gamete (animals): Sperm produced in the testes.
• Female Gamete (animals): Ovum produced in the ovaries
• Plant Male Gamete: Pollen produced in the anther
• Plant Female Gamete : Ovum in the ovule

Plant Pollination

• Self-pollination: Pollen from the same plant fertilizes the stigma.
• Cross-pollination: Pollen from a different plant fertilizes the stigma.
• Methods: Wind, water, insects, and animals.

Plant Seed Formation

• Stages: Pollination, germination, penetration, fertilization, seed development

This quiz covers the key features of asexual reproduction, including its definition, methods, and advantages and disadvantages. Explore various methods like binary fission, budding, and vegetative propagation, and understand the significance of cloning in the reproduction process.