Properties of Life and Reproduction

Properties of Life

• Orderly structure/arrangements are apparent.
• Evolutionary Adaptation: Species go through adaptation to be accustomed to the environment.
• Organisms respond to certain stimulants.
• Reproduction duplicates DNA to produce new individuals.
• Growth & development is the process of growth and acquiring traits.
• Energy processing is the process of acquiring nutrients.
• Regulation maintains internal balance/processes, also known as homeostasis.

Reproduction

• Procreation or breeding is reproduction
• Refers to the process of making new organisms, where new "offspring" are produced from their "parents".

Asexual Reproduction

• A mode of reproduction where new offspring is produced by a single parent.

Types of Asexual Reproduction

Binary Fission

• A single parent cell doubles its DNA, then divides into two cells.
• Usually occurs in bacteria.

Budding

• Small growth on the surface of the parent breaks off, resulting in the formation of two individuals.
• Occurs in yeast and some animals.

Fragmentation

• Organisms break into two or more fragments that develop into a new individual.
• The parent regrows its lost part.
• Seen in starfish, some worms, sponges, some plants, and other organisms.
• Fragmentation occurs when a piece of an organism grows into a new organism.
• Both the original and new organism have the same DNA.

Parthenogenesis

• An embryo develops from an unfertilized cell.
• Comes from the Greek words parthenos (virgin) and genesis (creation).
• Occurs in invertebrates, as well as in some fish, amphibians, and reptiles.
• Research showed that the Komodo dragon could produce young from unfertilized eggs.

Other Types of Asexual Reproduction

Spore Production or Sporulation

• A new individual forms from an aggregation of cells surrounded by a resistant capsule/spore.
• Later on germinates.

Vegetative Reproduction

• Does not involve formation of a seed.
• Each method involves taking a cutting of the parent plant, which will eventually grow identical to the parent.

Sexual Reproduction

• Requires 2 parents, male and female.
• Egg and sperm cells from these join to form an entirely new organism.
• Offspring produces are different from parent organism, hence producing a greater chance of variation within a species than asexual reproduction would.
• Improves chances that a species will adapt to his environment and survive.

Forms of Sexual Reproduction

Isogamy

• Fusion of similar gametes which are usually motile.
• Conjugation involves 2 filamentous gametes line side-by-side.
• One side will grow projections to form a bridge and allow fusion of protoplasts.

Heterogamy/Anisogamy

• Fusion of gametes with different sizes or forms.
• In humans, oogamy involves the union of a large immotile egg and a small motile sperm.

Hermaphroditism

• An individual having both a male and female reproductive organs.
• Clownfish start their lives as males then turn into females.
• A female clownfish lives with a group of males and mates with one of them.
• When she dies, her mate will become the next female.

Plant Reproduction

Sexual Reproduction in Flowering Plants

• Meiosis produces eggs and sperm.
• Seed germinates to produce plant.

Sexual Reproduction in Non-Flowering Plants

• Includes details of the General Life Cycle of a Moss.

Animal Reproduction

Reproductive Cycles and Patterns

• Ovulation is the release of mature eggs at the midpoint of female cycle.
• Most animals exhibit reproductive cycles related to changing seasons.
• Reproductive cycles are controlled by hormones and environmental cues.
• May reproduce asexually/sexually, or may alternate these methods.
• Fertilization depends on mechanisms that bring together sperm and eggs of the same species.
• Mechanisms of fertilization, union of egg and sperm, play an important part in sexual reproduction.

External Fertilization

• Eggs shed by female are fertilized by sperm in external environment.
• Occurs during spawning when the female releases the egg and the male releases the sperm in the same environment.

Internal Fertilization

• Sperm are deposited in or near the female reproductive tract, and fertilization occurs within the tract.
• All fertilization requires critical timing, often mediated by environmental cues, pheromones, and/or courtship behavior.

Animal Gamete Production and Delivery

• To reproduce sexually, animals must have systems that produce gametes.
• Most species individuals have gonads (sex organs), produce gametes.
• Some simple systems do not have gonads, but gametes form from undifferentiated tissue.
• Most insects have separate sexes with complex reproductive systems and Spermatheca.
• Spermatheca (Insects, female): Sperm is stored between the time of mating and the time an egg is fertilized.

Reproductive Anatomy

Ovulation

• Expels an egg cell from the follicle.

Corpus Luteum

• Remaining follicular tissue grows within ovary, forming a mass that secretes hormones that help to maintain pregnancy.
• If the egg is not fertilized, the corpus luteum degenerates.

Testes (Male Gonads)

• Consist of highly coiled tubes surrounded by connective tissue.
• Seminiferous tubules are where sperm form.
• Leydig cells produce hormones and scattered between the tubules.
• Production of normal sperm cannot occur at body temp. of most mammals.
• The testes are held outside the abdominal cavity in the scrotum, where the temperature is lower than in the abdominal cavity.

Ducts

• From the seminiferous tubules of a testis, sperm pass into coiled tubules of the epididymis.
• Takes about 20 days for sperm to pass through the 6 m long tubules of each epididymis of a human male.
• During ejaculation, sperm are propelled through muscular vas deferens and ejaculatory duct, and then exit the penis through the urethra.