Download Reproduction

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
Meiosis
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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
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
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.
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
Where does all this meiosis stuff
happen?
• In the gonads! –
– Males – testicles
– Females - ovaries
• Human Reproduction
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
The menstrual cycle
• The functioning of the reproductive system is
dependent on the cyclical fluctuation of
hormone levels that repeat regularly every 28
days.
If an egg is fertilized
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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
In the Beginning
• Gastrulation
• More human
Development