1. Animal Reproduction and Development
AP Biology Chapter 46 and 47

2. Asexual Reproduction Genes all come from one parent
Common to many invertebrates
Advantages
Enables animals to live in isolation – no need to locate mates
Organism can create numerous offspring in a short amount of time – rapidly colonize habitat
Advantageous in stable, favorable environments
Perpetuates successful genotypes precisely

3. Forms of Asexual Reproduction
Fission
separation of parent into two or more individuals of approximately equal size.
Budding
new individuals split off from existing ones
Fragmentation
Broken off body part grows into new individual
Regeneration of body parts
Parthenogenosis
Eggs develop without being fertilized
Queen Worker Drone

4. Forms of Asexual Reproduction
Parthenogenosis
Egg develops without being fertilized
Adults produced by parthenogenesis are haploid
Example: drone (male) bees form from single unfertilized egg and do not need to undergo meiosis to make their own new reproductive cells
SOMETIMES, in certain species, whether parthenogenesis occurs may be determined by season/conditions
Favorable conditions leads to asexual repro.
Everythings going well, why change?
Environmental stress leads to sexual repro
If conditions are bad, better hope some variety will come up with a solution!

5. Forms of Asexual Reproduction
Desert-grassland whiptail lizard is an all female species.
They reproduce by parthenogenesis
HOWEVER…ovulation is enhanced by courtship rituals that imitate sexual reproduction.

6. Sexual Reproduction
Creation of offspring by fusion of haploid gametes to form a zygote
Increases genetic variation
Probably enhances reproductive success when pathogens or other environmental factors change rapidly
If there’s variety, chances are better than someone will have a genetic solution to an environmental problem

7. Hermaphrodites
Each individual has both male and female reproductive systems
NOT ASEXUAL
Helps when finding a mate is not easy
Every individual encountered is a potential mate (as opposed to just ½ the individuals encountered)
Each partner donates sperm to female repro organs of the other.

8. Fertilization Joining of egg & sperm external internal
usually aquatic animals
internal
usually land animals

9. THE THEME THAT NEVER DIES…
WATER TO LAND!!!!
Keep this in mind as we talk about fertilization and reproductive structures…

10. External Fertilization
Requires environment where egg/zygote can develop without drying out.
The eggs are unprotected and vulnerable to water loss, etc.
Thus, almost always occurs in water/moist areas

11. External Fertilization
Parents may not even make physical contact
Eggs/sperm released into water
Timing is still important
Some do use specific mates and mating behaviors
Pheromones are used to draw animals together

12. External Fertilization
GENERAL rule
LOTS of zygotes produced
LITTLE parental care
Have lots of babies and hope at least a few of them survive
Very small proportion of zygotes survive to full development

13. Internal Fertilization
Land animals cannot just lay unprotected eggs in environment
WATER LOSS!!
Must protect
Gametes
Developing embryos

14. Internal Fertilization
Protects Gametes
Neither sperm nor egg is ever exposed to environment
Sperm placed directly inside the female
Protects Embryos
Embryos develop either:
Inside shelled eggs
Inside the female
Don’t come out until they can survive dry environment

15. Internal Fertilization
ALL internal fertilization requires
Sophisticated reproductive systems including organs that
deliver sperm
receptacles that receive, store and transport sperm to ripe eggs.
Cooperative behaviors leading to copulation
Uncharacteristic sexual behaviors are eliminated by natural selection
Example – female spiders eat males if they don’t use the proper reproductive signals

16. Internal Fertilization
Generally produces fewer zygotes than external
But proportion of zygotes that develop and survive is greater. This is because of:
greater protection of eggs/zygotes/embryos
Within a shell OR
Within the female
Due to better parental care of eggs and offspring
Don’t abandon young

17. Internal Fertilization
Two possible outcomes:
SHELLED EGGS to be laid on land
Reptiles, Birds
And 1 very small mammal group – montremes (platypus and spiny echidna)
Embryos develop inside the mother
Mammals (placental and marsupial)
Both animal types are called AMNIOTES due to the embryonic structures they share in common

18. AMNIOTES Amniotic eggs Shell is NOT the only part that protects
EXTRAEMBRYONIC MEMBRANES make the anmiontic egg successful
AMNION
surrounds baby with water
“little ocean”
Yolk Sac
Stored Food
Allantois
Waste sac
Chorion
Functions with allantois in GAS EXCHANGE

19. Quick Note on Anatomy of Egg Layers
CLOACA
Common opening to reproductive, urinary and digestive tracts
non-mammals and monotremes
Reptiles, birds, amphibians, fish

20. AMNIOTES Internal Development Mammals – Shelled egg not used, but
Amnion
Internal Development
Mammals –
both placental and marsupial
NOT monotremes (EGG LAYERS!)
Shelled egg not used, but
amnion present and
same extraembryonic membranes give rise to placenta, etc.

21. Mammalian Reproduction - Humans
Reproductive organs – from mammalian and human perspective, but apply to most vertebrates…

22. Male Reproductive Organs
Tubes, Tubes, Tubes!!
Best thought of as containers holding LOTS of TUBING.
Sperm develop in these tubes and then travel out of the body through the tubes

23. Male Reproductive Organs
Testes
Seminiferous Tubules
Sperm production
Epididymis
Sperm maturation
Vas Deferens
Carry sperm to urethra
Urethra
exit body

24. TUBES!

25. Cross section through Sem. Tubule
Seminiferous Tubules
Highly coiled tubes
Sperm are formed HERE
MEIOSIS HAPPENS HERE!!
Also contain cells (Leydig cells) which make male hormones
Testosterone and other androgens
Cross section through Sem. Tubule

26. Gametogenesis General term for creation of gametes SEX CELLS MEIOSIS
TWO TERMS
Spermatogenesis
Gametogenesis (meiosis) in males
Oogenesis
Gametogenesis (meiosis) in females

27. Spermatogenesis – MEIOSIS to create sperm
Least Mature
Also called
spermatogonium
Epididymis
Testis
Germ cell
(diploid)
Coiled
seminiferous
tubules 1°
spermatocyte
(diploid)
MEIOSIS I 2°
spermatocytes
(haploid)
MEIOSIS II
Vas deferens
Spermatids
(haploid)
Meiosis happens
Inside
Seminiferous
tubules
Most Mature
Spermatozoa
Cross-section of
seminiferous tubule

28. Spermatogenesis Spermatids Products of meiosis
4 created from each primary spermatocyte
Haploid
Immature sperm
Tailess
Sertoli cells
Provide nourishment to spermatids as they further develop into sperm at center of seminiferous tubule

29. 100 million produced per DAY
Mature sperm
100 million produced per DAY

30. Mature Sperm Sperm structure Head Mid-piece Tail Acrosome Nucleus
Contains enzymes to penetrate egg
Nucleus
Males genetic contribution
Mid-piece
Mitochondria
For energy - swimming
Tail
Microtubules
9+2

31. Fertilization Joining of sperm & egg sperm head (nucleus) enters egg

32. Cleavage zygote  morula  blastula establishes future development
gastrulation
morula
blastula

33. Glands of the Male Reproductive System
Prostate, seminal vesicles, Cowper’s (bulbourethal) glands
nutrient rich fluid to feed & protect sperm
buffer to counteract acids in vagina

34. Female reproductive system
Ovaries
produces eggs & hormones
Uterus
nurtures fetus; lining builds up each month
Fallopian tubes
tubes for eggs to travel from ovaries to uterus
Called OVIDUCTS in every other animal
Cervix
opening to uterus, dilates 10cm (4 inches) for birthing baby
Vagina
birth canal

35. Female Reproductive Organs
Ovaries
Each ovary contains many follicles
Follicle
One egg cell surrounded by follicle cells
Follicle cells nourish and protect developing egg
Follicle cells also produce primary female sex hormones
estrogens

37. Follicular Development

38. Mature Follicle

39. Ovulation

40. Oogenesis Oogonia Primary oocyte Secondary oocyte Ovum Diploid
Repeatedly divide to create more oogonia
mitosis
Primary oocyte
Cell that has entered into meiosis I
Secondary oocyte
Cell that has entered into meiosis II
Ovum

41. Oogenesis Unequal divisions
Make one really good egg and 2 polar bodies
Meiosis 1 completed
during egg maturation
ovulation
Meiosis 2 completed
triggered by fertilization

42. Reproductive hormones
LH & FSH
Testosterone
from testes
functions
sperm production
2° sexual characteristics
Estrogen
from ovaries
egg production
prepare uterus for fertilized egg
testes or ovaries

43. Estrous Cycles Estrous Uterine lining resorbed; not shed
More pronounced behavior changes
Copulation only occurs during ovulation
Dogs/Cats, etc.

44. Menstrual Cycles Uterine lining shed Less behavioral changes
Copulation may occur at any time in cycle