The document discusses different types of sex cells and fertilization methods in species. It describes eggs as large, immobile and few in number, providing nutrients, while sperm are small, mobile and produced continuously in large numbers. External fertilization involves releasing sex cells into water, while internal increases chances of fertilization. The document also covers parenting strategies like monogamy, polygyny, polyandry and differences in offspring development methods between viviparous placental, marsupial, oviparous, ovoviviparous and ovuliparous species.

2. Sex Cells
 Egg: big size, immobile, there are only a few. Inside
the egg there are nutrients for the embryo.
 Sperm cell: small size, mobiles, there
are many and are produced at all times.

3. Fertilization
 External fertilization: expel sex cells into the water.
How do they avoid the risk of not finding the other sex cell?

4.  Internal fertilization: sperm cells are expelled inside
the female body.
What is the advantage?

5.  This type of fertilization requires courtship and
intercourse.

7.  Disney Nature Minuto 24.

9.  Monogamy
 Polygyny
 Polyandry
An individual has one
partner during their
lifetime or at any one time.
A male has more than one
female.
A female has more than
one male.

10. Sexual Dimorphism
 Males and females of the same species are different.

11.  It doesn´t occur in every species...

12. Animals exhibit
different
strategies and
social
interactions..

13. Ovuliparous
 They release sex cells into the water and the embryo
develops there.

14. Oviparous
 The embryo´s development occurs inside an egg,
outside of the female´s body.

15.  Some of them incubate
the eggs.

16.  Others simply bury them!

17. Ovoviviparous
 They keep the eggs inside their body.

18. Viviparous
 The embryo´s development occurs inside the female´s
body (pregnancy).

19.  Marsupials: the offspring are born very inmature and
they are kept inside a “bag” in the mom´s body
(marsupio) where the mammal glands are. There they
complete their development.

20.  Placental: the development occurs inside the uterus.
The mother has a connection with the baby through
the placenta.

22. Development
 Direct development: they only change in size, but the
characteristics are pretty similar between an adult and
a baby.

24.  Indirect development (metamorphosis): adults are
very different from youngsters.

26. Reproductive Strategies
 “r” strategy: have a large number of offspring but they
don´t take care of them.

27.  “K” strategy: have few offspring but they look after
them until they reach the reproductive age (they
become adults).

31.  Some of them preffer
to get a nanny!