1. Infer Why might sexual reproduction, as opposed to asexual reproduction, produce a population better able to survive disease or environmental changes
Predict Why would you expect most species that employ external fertilization to reproduce in the water
Compare and Contrast What is the difference between a nymph and a pupa

2. Ch 28 Animal Systems II
28.3 Reproduction

3. Asexual Reproduction Many invertebrates and a few chordates
Requires only one parent
Can reproduce rapidly
Lack genetic diversity.

4. Types of Asexual Reproduction
Divide in two
Budding
Parthenogenesis
Females lay eggs that develop without being fertilized by a male.

5. Sexual Reproduction Involves meiosis, creates gametes
Male and female gamete join to create zygote
Genetic diversity
Requires two individuals of different sexes
Greater needs.

6. Most animal species that reproduce sexually have individuals that are either male or female
Some species are hermaphrodites
Some species switch sexes.

7. Reproductive Cycles
Some invertebrates have life cycles that alternate between sexual and asexual reproduction.

8. Blood flukes mature in the body of an infected person
Reproduce sexually and release embryos that pass out of the body in feces
Embryos develop into larvae and infect snails and reproduce asexually
Larvae infect people.

9. Jellyfish
Aurelia polyps produce medusas asexually by budding.

10. Medusas reproduce sexually by producing eggs and sperm that are released into the water.

11. After fertilization, the resulting zygote grows into a free-swimming larva.

12. Larva eventually attaches to a hard surface and develops into a polyp continuing the cycle.

13. Internal Fertilization
Eggs are fertilized inside the body of the egg- producing individual
Many aquatic and all terrestrial animals
Sperm may taken in from surrounding water, be gathered by the female, or deposited in side the female.

14. External Fertilization
Eggs are fertilized outside the body of the egg- producing individual
Aquatic invertebrate and vertebrates.

15. Development and Growth
After fertilization, the zygote divides through mitosis and differentiates
Development occurs under different circumstances in different species
Care and protection given to developing embryos also varies widely.

16. Animals may be oviparous, ovoviviparous, or viviparous.

17. Oviparous Embryos develop in eggs outside the parents’ bodies
Most invertebrates, many fishes and amphibians, most reptiles, all birds, and a few mammals.

18. Ovoviviparous
Embryos develop within the mother’s body, but depend entirely on the yolk sac of their eggs
Young do not receive any additional nutrients from the mother
Guppies and some shark species.

19. Viviparous
Embryos obtain nutrients from the mother’s body during development
Most mammals and some insects, sharks, bony fishes, amphibians, and reptiles.

20. Viviparous
Young are nourished by secretions produced in the mother’s reproductive tract in insects, and in some sharks and amphibians.

21. Viviparous Placenta In placental mammals.
Specialized organ that enables exchange of respiratory gases, nutrients, and wastes between the mother and her developing young
In placental mammals.

22. Most newborn mammals and newly hatched birds and reptiles look a lot like miniature adults.

23. As invertebrates, nonvertebrate chordates, fishes, and amphibians develop, they undergo metamorphosis
Metamorphosis
Developmental process that leads to dramatic changes in shape and form.

24. Aquatic Invertebrates
Have a larval stage that looks nothing like an adult
Swim or drift in open water before undergoing metamorphosis and assuming their adult form
May have multiple larval stages.

25. Terrestrial Invertebrates
Some undergo gradual or incomplete metamorphosis
Nymph
Immature forms that resemble adults
Lack functional sexual organs and some adult structures
Molt several times and gradually acquire adult structures.

26. Some undergo complete metamorphosis
Larvae look nothing like their parents, and they feed in different ways
Pupa
Stage in which an insect larva develops into an adult
Controlled by amount of juvenile hormone produced.

27. Care of Offspring
Species that provide intensive or long-term parental care give birth to fewer young than do species that offer no parental care
Type and amount of care varies greatly.

28. The Amniotic Egg
Provides a protected environment for an embryo to develop out of water
One of most important vertebrate adaptations to life on land
Reptiles, birds, and a few mammals.

29. Amnion
Fluid-filled sac that surrounds and cushions the developing embryo.

30. Chorion
Regulates the transport of oxygen from the surface of the egg to the embryo and the transport of carbon dioxide in the opposite direction.

31. Yolk sac Allantois Contains nutrient-rich food supply for the embryo
Stores waste produced by the embryo
Later fuses with the chorion.

32. Mammal Adaptations The three groups of mammals:
Monotremes
Marsupials
Placentals
All nourish their young with mother’s milk.

33. Monotremes
Lay soft-shelled, amniotic eggs that are incubated outside her body
Young are nourished by milk produced by the mother.

34. Marsupials
Bear live young that usually complete their development in an external pouch
Young spend months attached to a nipple drinking milk and growing inside.

35. Placentals
Nourished through a placenta before they are born and by their mother’s milk after they are born
Born at a fairly advanced stage of development.