Animal Reproduction Methods

Animal Reproduction

• Sexual reproduction: creation of offspring by fusion of haploid gametes, with advantages of increased genetic variation and adaptation to changing environments.
• Asexual reproduction: creation of offspring without fusion of egg and sperm, with advantages of rapid reproduction and genetic uniformity, but rare in vertebrates.
• Examples of animals that reproduce sexually: most vertebrates; examples of animals that reproduce asexually: sponges and hydra.

Fertilization

• Internal fertilization: occurs in a dry environment, with fewer gametes produced but higher survival chances.
• External fertilization: occurs in a moist environment, with more gametes produced but lower survival chances.

Reproductive Organs

• Gonad: organs that produce gametes (testes in males, ovaries in females).
• Male reproductive organs: sperm produced in seminiferous tubules, pass through epididymis, vas deferens, and urethra.
• Female reproductive organs: eggs produced in ovaries, travel through oviduct to uterus.

Gametogenesis

• Gametogenesis: production of gametes from germ cells.
• Spermatogenesis: formation of sperm, producing 4 sperm with no interruptions.
• Oogenesis: development of a mature egg, producing 1 egg with a prolonged process that stops at menopause.

Hormones in Reproduction

• Hormones involved in reproduction: GnRH, FSH, LH, testosterone, estrogens (estradiol and progesterone).
• Regulation of ovarian and menstrual cycles by sex hormones.
• Menopause: end of ovarian and menstrual cycles in females.

Neurons and Signaling

Structure of a Neuron

• Cell body: contains most of a neuron's organelles.
• Dendrites: highly branched extensions that receive signals from other neurons.
• Axon: longer extension that transmits signals to other cells at synapses.
• Synapse: junction between an axon and another cell.

Types of Neurons

• Sensory neurons: transmit information about external stimuli.
• Interneurons: integrate and interpret information.
• Motor neurons: transmit signals to muscle cells, causing contraction.

Glial Cells

• Glial cells (Glia): supporting cells that nourish, support, and regulate neurons.

Mechanisms of Signal Transmission

• Resting potential: membrane potential of a neuron not sending signals, with many open K+ channels and fewer open Na+ channels.
• Action potential: changes in membrane potential, signals conducted by axons, resulting in a massive change in membrane voltage.

Nervous Systems

Nerve and CNS

• Nerve: axons of multiple neurons bundled together.
• CNS: central nervous system, consisting of brain and spinal cord.
• PNS: peripheral nervous system, consisting of neurons carrying information in and out of CNS.

Structure of Brain

• Forebrain: includes cerebrum, thalamus, hypothalamus, and amygdala.
• Midbrain
• Hindbrain: includes cerebellum, medulla, and pons.

Cephalization and Neuronal Plasticity

• Cephalization: clustering of sensory organs at the front end of the body in bilaterally symmetrical animals.
• Neuronal plasticity: ability of the nervous system to be remodeled after birth.