Development and Reproduction

Development and Reproduction

• Development is a series of changes an organism undergoes throughout its life cycle.
• Reproduction is how animals produce offspring to continue their species.

Sexual Reproduction

• Involves the combination of genetic material from two different cells to produce offspring.

Advantages

• Results in diverse offspring due to genetic variation.
• Allows for selective breeding.
• Enables species to adapt to new environments.

Disadvantages

• Requires time and energy to find a mate.
• Impossible for isolated individuals.
• Searching for mates can expose individuals to dangers.
• Pregnancy can be lengthy.

Asexual Reproduction

• Involves only one parent, producing genetically identical offspring.

Types

• Budding is when a new organism grows on the parent's body via mitosis (e.g., hydra, yeast, cactus).
• Fission is cell division in prokaryotes, creating two identical cells (e.g., bacteria, E. coli).
• Fragmentation is when a parent organism breaks into fragments that grow into new organisms.
• Sporulation is the formation of spores from vegetative cells during unfavorable conditions.

Advantages

• Allows rapid population growth in favorable conditions.
• Requires only one parent.
• Is faster and more energy-efficient than sexual reproduction.

Disadvantages

• Does not lead to genetic variation.
• Species may only be suited to one habitat.
• Diseases can affect entire populations.

Plant Reproduction: The Flower

• Flowers are the reproductive structures in flowering plants, consisting of four major whorls.

Sepals

• The outermost whorl, collectively called the calyx.

Petals

• Located inside the sepals, collectively called the corolla, and are often brightly colored.

Stamen

• The male reproductive structure, consisting of the anther and filament.
  • Anther contains microsporangia that develop into pollen grains.
  • Filament supports the anther.

Pistil/Carpels

• The innermost whorl, the female reproductive structure, consisting of the stigma, style, and ovary.
  • Stigma receives pollen during pollination.
  • Style connects the stigma to the ovary.
  • Ovary contains ovules and eventually becomes the fruit.
  • Ovule contains megasporangia and eventually becomes the seed.

Stages of Animal Development

Gametogenesis

• Is stage of development that yields haploid gametes

Fertilization

• A single sperm cell combines with a single egg cell to form a zygote.
• A human egg cell is about 16 times larger than a human sperm cell.
• Eggs contain yolk to support embryo growth.
• Sperm contains tightly packed DNA, a flagellar tail, and mitochondria for movement.
• The plasma membrane of sperm contains bindin proteins for recognizing and binding to egg receptors.
• The acrosome in the sperm head contains digestive enzymes to degrade the egg's outer layers.

Cleavage

• Rapid mitotic cell divisions without increasing the embryo's overall size.
• Results in a blastula.

Gastrulation

• Rearrangement of cells in the blastula to form embryonic tissue layers.
• Forms three germ layers: ectoderm, mesoderm, and endoderm, which give rise to specific tissues and organs.
• Cleavage cell divisions can occur as frequently as every 10 minutes, versus the typical 18-24 hours.