Sexual reproduction in animals teacher

1. Step 3: Describe various methods of sexual and asexual reproduction in animal species

2. Reproduction (or procreation) is the biological process by
which new "offspring" individual organisms are produced from
their "parents".
Reproduction is a fundamental feature of all known life; each
individual organism exists as the result of reproduction. The
known methods of reproduction are broadly grouped into two
main types:
sexual and asexual

4. 1) Internal cross-fertilization
- Most mammals
(except for Australian montremes like the duckbill platypus)

5. As a reminder...
What are our observations and inferences about this based on what we see and
what we already know?

6. Sperm and egg cells are referred to as gametes
The fusion of these gametes is referred to as fertilization
Because each human gamete has 23 chromosomes, a zygote is formed
with a total of 46 chromosomes
How does it work?

7. The zygote divides through mitosis
and eventually becomes an embryo
All of these processes occur internally within the mother's
womb
The process is started by insemination
through copulation

8. 2) External Cross-fertilization
- most species of fish
- most species of amphibians
The details as to how this happen can vary...

9. How does it work?
eggs are shed from the female into an aquatic environment
Because of the flagella, sperm is adapted
for swimming in an aquatic environment
Sperm are shed onto eggs in order to fertilize

10. Specific Examples:
- some species produce floating egg and sperm
- some species attach the eggs to plants or other substrates

11. - some species (like salmon) deposit eggs into a hollow in a
gravel based stream and males swim over to fertilize

12. What are the risks with external fertilization?
- risk of predators and other external harms
- open space can lead to lower probability of
fertilization
- demands millions to billions of sperm to
compensate

13. - some species (cichlids) externally fertilize and then protect the
zygote in their mouth until they are developed (mouth brooding)

14. 3) Hermaphroditic cross-fertilization
A hermaphrodite is an organism that has both male and
female reproductive organs
- most snails
- earthworms
- some species of fish

15. How does it work?
There are many different kinds of hermaphroditic species
- Sequential Hermaphrodites: a type of species that is born as one sex and can change into the
opposite sex
The clown fish - All begin as male and the largest fish becomes the female

16. - Simultaneous Hermaphrodites: An adult species that contains both male and female
reproductive organs at the same time. Self-fertilization usually does NOT occur
Banana Slug - It is possible for banana slugs to mate as either male of female

17. 4) Hermaphroditic Self-fertilization
Also called Autogamy. When two gametes are fuzed
together from the same hermaphroditic individual
- tape worms
- most internal parasites

19. 1) Parthenogenesis
- some small invertebrates (bees, scorpions, aphids, etc)
- some vertebrates (fish, amphibians, reptiles)

20. How does it work?
a form of asexual reproduction in which growth and
development of embryos occur without fertilization
Occurs naturally in some species but is artificially induced in
other species
This happens in two main ways

21. - apomictic parthenogenesis:
This process occurs without meiosis
Mature egg cells are produced by mitotic divisions, and
these cells directly develop into embryos
The offspring produced are full clones of their mother

22. - automictic parthenogenesis:
This process involves meiosis
the offspring differ from one another and from their mother.
They are called half clones of their mother
The other half of the alleles are developed through complex
biological processes

23. Bonnethead
A bonnethead, a type of small hammerhead shark, was found to have produced a pup,
born live on 14 December 2001 at Henry Doorly Zoo in Nebraska, in a tank containing
three female hammerheads, but no males. The pup was thought to have been conceived
through parthenogenic means.

24. 2) Budding
- Hydra, coral, sponges

25. How does it work?
form of asexual reproduction in which a new organism
develops from an outgrowth or bud due to cell division at one
particular site
The new organism remains attached as it grows, separating
from the parent organism only when it is mature, leaving behind
scar tissue.

26. the newly created organism is a clone and is genetically
identical to the parent organism.
Hydra reproducing
asexually through the
process of budding

27. Summary:
Make a list of the advantages and disadvantages of all of the different types of sexual
and asexual reproduction in animals