animal reproduction a. russo-neustadt csula. asexual versus sexual reproduction
TRANSCRIPT
Animal Reproduction
A. Russo-Neustadt
CSULA
Asexual
versus
Sexual Reproduction
Asexual Reproduction
Asexual Reproduction – reproduction that produces individuals who are genetically identical to the parents
No sperm and egg fusion Examples – budding in
hydra, fragmentation & regeneration in sea stars, fission in Sea Anemones
Budding
Fission
Sea Star Fragmentation
Linkia genus
Advantages of Asexual Reproduction Isolated/sessile species Time efficient Conservation of energy Like parent/Like offspring (instant
adaptation)
Huge Disadvantage of Asexual Reproduction What if environmental conditions change –
become unfavorable?
Sexual Reproduction
Sexual Reproduction reproduction that produces offspring who are
genetically different from either parent (genetic variability)
requires production of gametes that fuse to form a fertile egg- Example – humans, frogs, earthworms
Humans
Frogs
Earthworms-Hermaphrodites
Advantages to Sexual Reproduction
Genetic variation Environmental Adaptation
Disadvantages to Sexual Reproduction
Isolated/solitary/non-motile animals One potential solution for a few select
animals is the evolution of Hermaphroditic characteristics (earthworm, tapeworm)
Sexual Reproduction
Internal versus
External Fertilization
External Fertilizationused by aquatic animals
Internal Fertilization
Used by some aquatic animals and all terrestrial animals
Requires copulation – and specialized organs
Internal Fertilization
Embryological development post-fertilization can be
Oviparous
Ovoviviparous
Viviparous
Internal Fertilization
oviparous – eggs laid and hatch outside the body (examples – birds, reptiles)
ovoviviparous – eggs develop inside of female’s body, but do not receive nourishment from her (example – some sharks)
Interuterine CanabolismSandtiger (embryophagy)Great White (oophagy)*others are viviparous and
oviparous
Viviparous – embryos develop in female’s body and receive nourishment directly from her, often using a placenta (example – mammals)
What happens after animals are born or hatched?
Young that hatch or are born can be Precocial
– highly developed and able to move about and feed themselves, “miniature adults” (example – reptiles)
Young that hatch or are
born can be Altricial - immature and require
considerable parental care to survive
Note the energetic trade off between parental investment in lots of gametes versus significant parental care of young
Human Reproduction
There are two basic types of reproductive system organs –
Gonads = primary sex organs = essential sex organs; ovary and testis1. Produce the gametes
2. Produce the sex hormones that –
Regulate the reproductive process
Regulate development and function of the other reproductive system organs
Types of reproduction system organs - continuedSecondary sex organs = accessory sex
organs; involved in -
a. transport
b. protection
c. nourishment
of the gametes, embryo or young
Human Reproductive Anatomy
The human male primary sex organ and associated organs
Testes = primary sex organ; spermatogenesis occurs in seminiferous tubules, testosterone production occurs in cells of Leydig
Site of final sperm maturation, takes several weeks
Sperm transport – through inguinal canal to abdominal cavity out urethra, fluids added along the way
The human female primary sex organ and associated organs
Ovary = primary sex organ; egg production and estrogen and progesterone production all occur within the follicles
Oviduct = fallopian tube, site of fertilization of the egg, transport of egg from ovary to uterus
uterus
Endocrine Control of Ovary and Testis Function
Hormones control reproductive function