Asexual Reproduction Overview

Asexual Reproduction

• Asexual reproduction creates offspring genetically identical to the parent
• It occurs in the absence of a mate
• Types include binary fission (mitosis), budding, spores, fragmentation, and vegetative propagation (propagation)

Binary Fission (Mitosis)

• The cell replicates its DNA
• The cytoplasm elongates and divides
• Two daughter cells form

Budding

• The parent produces a smaller version of itself (bud)
• The bud either detaches and becomes a new individual or stays attached and forms a colony

Spores

• An organism produces many spores that act like seeds
• Spores can develop into new individuals

Fragmentation

• A piece of an organism breaks off
• The fragment develops into a new individual

Vegetative Reproduction (Propagation)

• Plant reproduction that does not involve seeds
• This includes fragmentation (cutting), runners, grafting, tubers, and suckers

Sexual Reproduction

• Reproduction involves the union of male and female reproductive cells (gametes)
• Genetically varied offspring are produced by two parents

Advantages of Asexual Reproduction

• Large numbers of offspring
• Little to no energy needed to find a mate
• Little to no parental care
• Only one organism needed

Disadvantages of Asexual Reproduction

• Offspring are clones (susceptible to diseases or harmful mutations)
• Extreme temperatures can wipe out entire colonies
• Offspring compete for resources like food and space

Advantages of Sexual Reproduction

• Genetic variation, allowing more organisms to survive in changing environments

Disadvantages of Sexual Reproduction

• Takes more time (finding a mate, fusion of gametes)
• Exposure to conditions (disease, predators, harsh environment) when finding a mate
• Fewer offspring
• Offspring take longer to mature
• Offspring may need to be raised

Gametes

• Sex cells produced by organisms
• Contain half the number of chromosomes in a normal body cell
• Haploid

Male Gametes in Animals

• Sperm cells
• Produced in the testes

Female Gametes in Animals

• Egg cells (ova)
• Produced in the ovaries

Male Gametes in Plants

• Pollen
• Produced in the anther

Female Gametes in Plants

• Ovum
• Egg cells
• Produced in the ovule

Meiosis

• The process of producing gametes

Haploid

• Half the genetic material (n)

Diploid

• Double the genetic material (2n)

Human Haploid Number

• 23

Human Diploid Number

• 46

Stages of Meiosis

• 8 stages (4 divisions with 2 stages each)
• Results in four haploid daughter cells which are all genetically different

Meiosis I

• Prophase I: Chromosomes condense, nuclear membrane disappears, homologous chromosomes pair up and cross-over occurs.
• Metaphase I: Spindle fibers attach to chromosomes, homologous pairs line up in the middle of the cell (2 lines).
• Anaphase I: Spindle fibers contract, pulling homologous chromosomes to opposite poles of the cell.
• Telophase I (and cytokinesis): Spindle fibers break up, nuclear membrane may reform, and two cells are now haploid.

Meiosis II

• Prophase II: Centrioles move to opposite sides and spindle fibers reattach.
• Metaphase II: Spindle fibers line up chromosomes in the middle of the cell (single file).
• Anaphase II: Spindle fibers contract and pull sister chromatids to opposite poles of the cell.
• Telophase II (and cytokinesis): Spindle fibers break up, nuclear membrane reforms, and cytokinesis makes two cells from one, resulting in four haploid cells

Fertilization

• Fusion of male and female gametes forming a single diploid cell (zygote)

Fertilization in Humans

• Sperm meets egg in fallopian tube
• Sperm reacts with egg membrane, breaking it down
• Their cell membranes fuse, and the sperm nucleus enters the egg
• The egg's membrane hardens to prevent other sperm from entering
• Nuclei of egg and sperm combine forming the diploid zygote

Plant Pollination

• Transfer of pollen from anther to stigma
• Methods include wind, water, insects, and animals

Self-pollination

• Pollen arrives on the stigma of the same plant

Cross-pollination

• Pollen lands on the stigma of a different plant (but the same kind)

Plant Seed Formation

• Pollination: Pollen transferred to stigma
• Germination: Pollen tube grows to egg cell
• Penetration: Pollen tube reaches ovule
• Fertilization: Nuclei fuse
• Seed formation: Fertilized ovule forms seed

This quiz explores the various forms of asexual reproduction, including binary fission, budding, spores, fragmentation, and vegetative propagation. Gain insights into how these processes allow organisms to reproduce without the need for a mate, resulting in genetically identical offspring.