Reproduction

ASEXUAL REPRODUCTION

Asexual Reproduction reproduction by MITOSIS only one parent offspring is genetically identical to parent organism rapid and results in the production of large numbers of offspring

Binary Fission Bacteria, some protists (ameba, paramecium, algae) Parent organism divides into 2 equal parts

Budding parent organism divides into two UNEQUAL parts The buds may break off and live independently Some buds may remain attached to the parent and form a colony

Spore formation (sporulation) Spores are single, specialized cells produced by mitosis When spores are released from the parent organism, the spores germinate and grow to form new individuals Spore germination requires an environment that is warm, has nutrients and moisture

Regeneration The ability of an organism to regrow lost body parts Regeneration decreases as an animal becomes more complex

Vegetative Propagation A type of regeneration that occurs in plants Complete new plants develop from a part of the parent plant (root, stem, leaf)

1. Bulbs Enlarged underground stem surrounded by leaves and contains stored food New bulbs form by the base of the leaf

2. Tuber Enlarged underground stem with stored food Buds (“eyes”) can develop into new plants

3. Runners Stems that grow along the ground New roots form where the stem meets the ground and develop into a new plant

4. Rhizomes Stem that grows sideways underground or underwater

Artificial Vegetative Propagation

1. Cuttings Any part of the plant (stem, leaf, root) is used to produce a new individual

2. Grafting A stem is removed from one plant and joined permanently to another plant Stock: provides the root system Scion: added piece

Advantages Plants that grow from seeds do not always show the same characteristics Faster Higher yields of fruits

SEXUAL REPRODUCTION IN PLANTS AND ANIMALS

Sexual Reproduction Reproduction by combining the female gamete and male gamete Involves fertilization and meiosis – Meiosis: formation of gametes Produces offspring that are genetically different from both parents.

Advantages and Disadvantages Asexual Reproduction – Advantages: Rapid Populating: produce large quantities of offspring quickly No True Investment: quick and inexpensive process in terms of time and number – Disadvantages: No Diversity: All offspring are genetically identical Prone to Extinction: same traits = same weaknesses Can’t Adapt: can’t change due to environmental changes

Advantages and Disadvantages Sexual Reproduction – Advantages: Offspring are genetically different from one another – Disadvantages: Requires two parents with a large expenditure of energy Requires more time to produce offspring

TYPES OF FERTILIZATION

External Fertilization External fertilization is the process in which a sperm joins with an egg outside of the body.

Internal Fertilization Internal fertilization is the process in which a sperm joins with an egg inside of the body.

HUMAN REPRODUCTION

Male reproductive system Testes – the male gonad; produce sperm and testosterone Located outside of the body in structure called the scrotum Lower temperature is best for sperm production and storage Testes are 3°C lower than body temp

Male reproductive system Mature sperm are stored in the epididymis The sperm is transported from the testes (testicles) to the vas deferens vas deferens: tubes that connect to urethra

Glands that add fluid are the Cowper’s gland, seminal vesicles and prostate Fluid nourishes and transports sperm, protects sperm from acidity of female reproductive tract Sperm + seminal fluid = semen Male reproductive system

Female reproductive system Ovaries – the female gonad; produce egg cells (ova) and hormones estrogen and progesterone Oviduct (fallopian tube) - a tube that carries the egg cell (ovum) to the uterus; ****site of fertilization of the egg cell Cilia draws ovulated egg cell into the oviduct

Female reproductive system Uterus – a thick, muscular, pear shaped organ (aka womb) – A baby develops here Cervix – narrow neck that is the opening to the uterus Vagina – the birth canal

Menstruation  Menstrual cycle – a series of changes controlled by hormones that help prepare the female uterus for a possible pregnancy  The cycle is controlled by hormones of the pituitary gland and ovaries  The menstrual cycle occurs in 4 stages

Menstrual Cycle  begins at puberty (usually between ages 10 & 14)  usually lasts 28 days, but can vary due to illness & other factors  stops when a women is pregnant  stops permanently during ages (menopause)  humans & primates are the only mammals to have a menstrual cycle

Stage 1 - Follicle stage (lasts~10-14 days)  ovarian hormones (estrogen and progesterone) are in low concentrations  pituitary produces FSH which causes a follicle (egg cell capsule) to form  as the follicle grows it makes increased amounts of estrogen  estrogen has negative feedback on the pituitary to stop FSH  estrogen causes the uterine lining (endometrium) to grow thicker

Stage 2 – Ovulation (middle of cycle)  increased estrogen from the follicle stimulates the pituitary gland to produce LH  LH surge causes the follicle to rupture and the egg cell is sent to the oviduct=ovulation

Stage 3 – Corpus Luteum  ruptured follicle heals inside the ovary forming the corpus luteum  Yellow body  corpus luteum produces progesterone  progesterone maintains the added growth of the uterine lining

If fertilization takes place:  An embryo in the uterus will secrete a chemical called hCG  hCG prevents the corpus luteum from decomposing which maintains progesterone levels  The uterine lining is not shed  hCG is the chemical that is detected by pregnancy tests

Stage 4 - Menstruation  if an embryo is not present, approximately 2 weeks after ovulation the corpus luteum decomposes  estrogen & progesterone levels decrease  uterine lining is shed and moves out through the vagina (menstruation)  pituitary increases the release of FSH & a new follicle matures

Fertilization:  IF fertilization takes place, it occurs in the oviduct  The egg cell is viable for approximately 24 hours after ovulation

Implantation  After approximately a week, the developing embryo is implanted into the uterus  Embryo: conception to 8 weeks

Embryonic Development  A series of cell divisions and differentiation into various tissues and organ systems

Embryo : a multicellular organism in the early stages of development

Differentiation  the changing of unspecialized embryonic cells into the specialized cells, tissues and organs of a multicellular animal  The ectoderm, mesoderm, and endoderm differentiates to form tissue and organs systems

Differentiation  Each cell contains the same genes, but different genes are expressed in different cells (embryonic cells use different portions of their genetic information)  The type of cell that forms through differentiation is controlled by genes, hormones and cell location

Prenatal Development zygote  multiple identical cells  differentiated cells (tissues)  organs  organ systems  individual

Prenatal Development The single-celled zygote forms a multicellular organism with specialized cells through the processes of: mitosis and differentiation

Prenatal development  When the zygote is implanted in the uterine wall a temporary organ called the placenta is formed from maternal and embryonic tissues Placenta

Prenatal development  The developing embryo is attached to the placenta by the umbilical cord  This cord contains blood vessels Placenta Umbilical cord

Placenta: site of diffusion  Oxygen & nutrients diffuse from the mother’s blood vessels, across the placenta, and into the baby’s blood vessels  Wastes diffuse from the baby’s blood vessels into the mother’s blood vessels

Prenatal development  The fetus is surrounded by a membrane called the amnion which is filled with amniotic fluid  The fluid protects the fetus by giving it a stable environment and absorbing shock

Prenatal development  By the end of the 8 th week of pregnancy the embryo is called a fetus and all of the major structures are present

Human gestation  the period between fertilization and birth  approximately weeks  When gestation is complete the baby passes through the cervix and then through the vagina