fertilization and developmnt

1. Sexual Reproduction

2. Sexual Reproduction
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Method of reproduction requiring genetic contribution from two
parents and producing genetically unique offspring
Three stages of sexual reproduction:
1)Mating – Process by which gametes arrive in the same place
at the same time.
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● Humans = intercourse
Plants = fertilization
Fish = spawning
2)Fertilization – Union of egg and sperm cells
3)Development – Growth and specialization into the organism

3. Mating
● Timing is everything
– Many organisms mate during specific mating seasons
to increase the chance of finding a suitable mate and
increase the likelihood of offspring's survival.
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● Ex. Many animals mate in the winter or early spring
so offspring will be born when the weather is less
harsh
Ex. Marine and aquatic organisms may release eggs
and sperm in sync with the moons cycle

4. Mating
● Mate selection
– In order to produce the most successful offspring
possible organisms may choose their mate based on:
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● Ability to provide for the offspring
Desirable genetic traits
Maximum genetic diversity
– Organisms may attempt to win a mate through mating
displays or competition
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● Colourful plumage
Mating dance/show
Chocolate and flowers

5. Fertilization
● There are three ways for the gametes to unite:
1)Internal Fertilization
● Sperm are deposited inside the body of the female
● Common in land-dwelling organisms
● Embryo develops and is nourished inside mothers
body or inside a hard shelled egg

6. Fertilization
2) External Fertilization
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● Sperm and egg meet outside of the parent bodies
Common in aquatic and marine organisms
Ex. Spawning fish

7. Fertilization
3) Pollination
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● Type of internal fertilization found in plants
Plants may self-pollinate or cross-pollinate
Pollen contains the male gametes
May require pollinators (eg. birds, bugs, wind)

8. Flower Parts
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A – Stigma / Style
B – Anther
C – Petal
D – Sepal
E - Ovary
F – Stem
G – Ovules
H – Filament
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9. Pollination
1) Pollen grains carry the sperm cells of the plant to the
sticky stigma of the female reproductive structure
2) A pollen tube grows from the pollen grain down the style
to deliver sperm to the egg cells in the ovules
3) Fertilization occurs
4) Zygote develops and is nourished by stored nutrients
inside a seed
5) Seed germinates and grows into a mature plant when
conditions are optimal

10. Fertilization
Internal Fertilization
● Advantages
–
– More offspring survive due to
protection and parental care
Successful fertilization more likely
● Disadvantages
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Requires more energy to find a mate
Fewer offspring produced
Large investment from female parent,
may leave her vulnerable
●
External Fertilization
Advantages
–
–
–
Little energy needed to find a mate
Many offspring produced
Offspring not in competition with
parents
● Disadvantages
–
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– Many gametes do not survive or are
not fertilized
Zygotes and embryos are unprotected
No parental care mean many offspring
do not survive to adulthood

11. Embryonic Development
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After fertilization occurs the zygote begins the process of
mitosis and divides rapidly
Week 1 – Morula: cluster of cells
Week 2 – Blastula: hollow ball of cells
Week 3 – Gastrula: ball of cells organizes into layers which
will later specialize

12. Embryonic Development

13. Embryonic Development
●Gastrulation – Layers of the gastrula differentiate
into endoderm, mesoderm and ectoderm

14. Embryonic Development
Trimester Main Events Gestational age Size
First
Second
Third
Use text pg 218-219 to complete the table below