Organismal Development Part 3 Male Animals

Important concepts from previous units: Mitochondria provide chemical energy (ATP) for cells by performing cellular respiration using sugars. Pheromones are a form of long distance communication between organisms using chemical attractants. Matter and energy for growth and development comes from the environment.

Mitochondrion Intermembrane space Outer membrane Free ribosomes in the . Mitochondrion Intermembrane space Outer membrane Free ribosomes in the mitochondrial matrix Inner membrane Cristae Matrix Mitochondrial DNA 100 nm

Phermones

Hermaphrodites – Organisms possessing both sexual organs Hermaphrodites – Organisms possessing both sexual organs. Most species cannot self-fertilize. Sequential Hermaphrodites - The organisms can change sexes based on environmental pressures. Protogynous (“proto”; “alpha” means “first”; “gyn” refers to females) The Alpha female becomes male. Protandrous – (“andro” refers to males) The Alpha male becomes female. This guarantees that the most fit genes are passed on to the next generation.

Earthworms are hermaphrodites

Protogynous (Male is blue)

II. Mechanisms for sexual reproduction: A. Fertilization - The fusing of haploid sperm and egg to create a diploid zygote. 1. Externally – Fertilization occurs outside the body. (This occurs in fish and amphibians.) 2. Internally – Fertilization occurs internally. (This occurs in most animals including reptiles, birds, and mammals.)

External Fertilization

Internal Fertilization required

III. Pheromones – Chemicals that are released into the outside environment to attract a mate or mark a territory. MATE ATTRACTANTS

Spermatogenesis – This is the making of sperm. Spermatogonia – These are the cells that make sperm (4 of them) by undergoing the two divisions meiosis. Sperm structure: The Head contains the: Nucleus - Site of the DNA. – It has 23 Chromosomes in humans. (It is n- haploid.) Acrosome – The tip of the head that contains digestive enzymes used to eat through the protective jelly surrounding the female egg. Midpiece – This part contains mitochondria for making energy (ATP) to power the swimming of the tail. Tail – It is a flagella composed of microtubules from the cytoskeleton.

Spermatogenesis Epididymis Seminiferous tubule Testis Cross section of seminiferous tubule Spermatogonium Mitotic division, producing large numbers of spermatogonia Sertoli cell nucleus Differentiation and onset of meiosis I Primary spermatocyte (in prophase of meiosis I) Meiosis I completed Secondary spermatocyte Meiosis II Lumen of Seminiferous tubule Early spermatids Spermatids (at two stages of differentiation) Differentiation Sperm cells Neck Head Midpiece Tail Plasma membrane Acrosome Nucleus Mitochondria

Androgens – These are the male hormones. Male hormonal pattern Androgens – These are the male hormones. Primary sex characteristics – This refers to the ABILITY to make sperm. (This occurs at adolescence.) Secondary sexual characteristics – This are the “traits” of men such as facial hair, muscle mass, deep voice. Secondary characteristics start at puberty with the release of GnRH, from the hypothalamus, to the pituitary and continues until death usually. (This is why it is non-cyclic.) These hormones are not released in a cyclic pattern like female hormones are.

Secondary Sexual Characteristics