Reproduction

Invertabrates – How do they “Do It”• Hydra – Budding - asexual• Earthworm – hemaphroditic and exchange

sperm with each other – the fertilized egg capsule gets dropped off in the soil

• Grasshopper – separate sexes -Female grasshoppers deposit fertilized eggs in batches in the ground, the female uses four horn-like appendages at the tip of the abdomen, and twists her body and forces her ovipositor into the ground - metamorphosis

Vocab

• Regeneration – lobster claw or sea star arm grows back

• Parthenogenesis – egg cells can become an organism without sperm – ie bees

• Haploid – n – one set of chromosomes (unfertelized egg)

• Diploid – 2n - two sets of chromosomes

Males

Side View

Male Reproductive system

• Major functions• Produces sperm• Produces semen – the fluid vehicle that acts

as nourishment for sperm as they make their way through the female reproductive system

• Produces Testosterone – male hormone for secondary sex characteristics and tells the body to make testosterone

Feedback Mechanism

Female Reproductive system

Side view

Meiosis

• How we get SEX CELLS• Gametogenesis• Two division stages – Meiosis I and Meiosis II• Meiosis I is the reduction phase – Meiosis II is

the division stage (similar to mitosis)

Gametogenesis

Meiosis I

• Interphase I – DNA replicates, sister chromatids are joined by a centromere

• Prophase I – Chromosomes line up in homologous pairs in a process called synapsis forming a tetrad – crossing over occurs during this stage.

• Metaphase I – Tetrads move to the “equator” or metaphase plate – attach to spindle fibers

• Anaphase I – homologous chromosomes separate (keeping chromotids intact)

• Telophase I – events occur in the reverse order from the events in prophase I…spindle broken down two new cells are formed, chromosome number reduced in half

Non disjunction

• During Meiosis I – an abnormality that can happen is that one pair of tetrads doesn’t separate so both chromosomes go to one side while the other side doesn’t get a copy of that chromosome at all – this is the cause of down’s syndrome.

• non disjunction animation

Meiosis II

• Meiosis II can occur immediately (in males) can be put on hold (in females)

• Names are the same – prophase II, metaphase II, anaphase II, telophase II

• Similar to mitosis the chromosomes line up in the middle (NOT tetrads) – chromotids separate to opposite poles – (only DNA doesn’t get replicated BEFORE this stage!)

Vocab

• Meiosis – making sex cells• Gametogenesis – making sex cells– Gamete = sex cell

• Spermatogenesis – making sperm– Sperm = male sex cell

• Oogenesis – making egg– Ova = female sex cell

The menstrual cycle

• The functioning of the reproductive system is dependent on the cyclical fluctuation of hormone levels that repeat regularly every 28 days.

Feedback Mechanism

If an egg is fertilized

• Must be fertilized in the oviduct• 24 – 48 hours after ovulation• Pregnancy occurs• Fertilized egg travels down oviduct and

implants into uterus• Most development occurs within the first

trimester (month 1 – 3)• The last trimester is mainly for growth

Genetic Variation

• If a plant has seven pairs of chromosomes – and there are two different ways it can line up at the equator…how many sperm are possible?

• 2n = 27 = 128 combinations of sperm – also then 128 combinations of egg how many possible zygote

• 128 x 128 = 16,384 possible outcome

Human variation

• We have 23 chromosome – 2n = 223 = over 8 million combinations

• 223 x 223 = 70 trillion different zygotes are possible.

In the Beginning

• Gastrulation

• More human Development