Sexual Reproduction EXTERNAL INTERNAL

Sexual Reproduction Requires two parents (unlike asexual reproduction) Species must mate with members of their own species

Sea Urchin Example Eggs and sperms are released into water where the fertilization occurs Green and Purple urchins (different species) lives side by side

Sea Urchin Example Sperm and egg cells of all species of sea urchins have unique proteins and sugars on their surfaces

Sea Urchin Example Sperm and egg cells of all species of sea urchins have unique proteins and sugars on their surfaces Fertilization in a particular species of sea urchin will occur only if the right sugar meets the right protein of that species (just like a key and a lock)

Sea Urchin Example Because sea urchin eggs are transparent, scientists can observe and study how the fertilized egg begins to develop and gain a better understanding of fertilization among other animals.

Three Stages of Sexual Reproduction MATING FERTILIZATION DEVELOPMENT

Mating The process by which gametes arrive in the same place at the same time. Different times for different animals (mating seasons) Different places for different animals (water, land, steep mountains )

Modes of Fertilization Two ways for the union of sperm and egg cells to occur: EXTERNALY or INTERNALY There must be enough nutrients for the embryo The temperature must be warm enough so that proteins in the developing embryo will function properly There must be sufficient moisture so that the embryo does not dry out. The embryo must be protected from predators and from other environmental

External Fertilization A sperm and an egg unite outside the bodies of the parents Common in animals and plants living in water

External Fertilization A sperm cell and an egg cell unite outside the bodies of the parents Common in animals and plants living in water

External Fertilization Common in animals and plants living in water Water transports the gametes

External Fertilization ADVANTAGES No energy required to find a mate Large number of offsprings produced No competition for food from offspring and parents DISADVANTAGES Many offsprings will not survive outside the parents bodies Parents do not care for them

Internal Fertilization Sperm cells are deposited inside the female s body where they meet an egg cell

Internal Fertilization The embryo develops and is nourished inside the mother s body for a period of time protection from predators

Pollination Is that variation, or inherited genetic differences in a species, is called genetic diversity.

Pollen Transport Is that variation, or inherited genetic differences in a species, is called genetic diversity.

4.1 The Male Reproductive System The male reproductive system is designed for two purposes: to produce sperm and to deliver the sperm to the egg.

SEXUAL CHARACTERISTICS Humans have primary and secondary sexual characteristics. Primary Secondary all the structures that produce sperm cells and deliver them to the female. characteristics that are not necessary for sexual reproduction

Secondary Sexual Characteristics Secondary sexual characteristics do not develop until puberty.

Secondary Sexual Characteristics Puberty is the period in the development of a human during which he or she becomes sexually mature and able to reproduce.

Secondary Sexual Characteristics PUBERTY in males starts at: 11 and ends at around age 19 include a growth spurt

Secondary Sexual Characteristics PUBERTY in males start at: include a growth spurt emergence of facial, underarm, and pubic hair;

Secondary Sexual Characteristics PUBERTY in males start at: include a growth spurt emergence of facial, underarm, and pubic hair; the deepening of the voice.

Structure of a Human Sperm Cell The design of the human sperm cell tells you about its function. The head contains the haploid nucleus with 23 chromosomes. The sperm cell is very streamlined and built to move. The whip-like tail is called the flagellum and propels the sperm

Male Reproductive Structures There are two testes that hang outside and are protected by a sac called scrotum

Male Reproductive Structures The testes produce and nourish the sperm, and also produce testosterone

Male Reproductive Structures Each testis contains a mass of coiled tubes called seminiferous tubules, which contain diploid cells that undergo meiosis to produce haploid sperm

Male Reproductive Structures Epididymis is the place where mature sperm are stored.

The Path of the Sperm Cell Sperm travel to the outside through two tubes attached to the epididymis called the vas deferens

The Path of the Sperm Cell the vas deferens are connected to urethra

The Path of the Sperm Cell Urethra is used to transport sperms and urine (not at the same time!!)

The Path of the Sperm Cell The penis is the organ that: contains the urethra enters the female/male during sex ejaculate sperms inside the body of the female/male during sex

Sperm Production and Development Sperm cells start out as diploid cells on the inside surface of a seminiferous tubule

Sperm Production and Development When they pushed closer to the centre of the tubule, they undergo meiosis to become haploid cells

Sperm Production and Development Males with a healthy reproductive system can produce 200 to 300 million sperm each day.