1. Why do animals reproduce?
Here is the life story of Mimi. Let us see what stages she has experienced. 1 2 3 4 5 6 7
Mimi was born.
One year old
One-month old
Three-month old
Mimi gave birth.
Mimi became older.
Mimi finally died.

2. Why do animals reproduce?
Let us see what stages Gigi, the bird, has experienced. 1 2 3 4 5 6
Growth
Laying eggs
Birth
Death
Become adult
Old stage

3. Why do animals reproduce?
How do animals change at different stages of life？
Birth
Newborn animals are small in size.
Growth
Animals mature. They become bigger and stronger.

4. Why do animals reproduce?
How do animals change at different stages of life？
Old age
Death
Animals become weaker and are easier to get sick.
As the animals’ health gets worse, their body functions begin to fail and finally they die.

5. Why do animals reproduce?
How do animals make their species continue 延續 ?
By reproduction. 繁衍
All animals experience the stages of ________, ________, _________ and
________. Animals ___________ to ensure their species do not extinct (絕種).
birth
growth
old age
death
reproduce

6. What similar characteristics特徵do the kitten and its mother have?
The kitten looks almost the same as its mother. E.g. Both of them have whiskers鬚and paws.爪

7. Do other animals have their parents’ characteristics?
Yes
Red-crowned crane丹頂鶴
and its young

8. Do other animals have their parents’ characteristics?
Yes
A woman and her child

9. If animals cannot pass on their characteristics to their offsprings,後代
what will happen?
The characteristics enable 確保animals to survive in their living environment. If their offsprings do not have such characteristics, it is hard for them to survive and their species will become extinct eventually.
Animals can / cannot pass on their characteristics to their offsprings.

10. How do animals reproduce?
Viviparous animals (胎生動物)
Sperm
ovum
ovary 卵巢
testis 睪丸
After mating交配, the sperm combines with the ovum to form a fertilised egg.受精卵
The fertilised egg develops into an embryo胎兒in the mother’s womb. 子宮
Mature sex organs produce sperms精子and ova卵子.

11. How do animals reproduce?
The foetus 胎兒gets nutrients 營養from its mother.
When the foetus is fully developed, the mother gives birth to the baby.

12. How do animals reproduce?
What is child of viviparous animal 胎生動物feed on?
Its mother’s milk. 母乳
List three examples of viviparous animals.
Cats, dogs, sheep etc.
The embryo胚胎 of viviparous animal develops inside / outside
the mother’s body. The mother gives birth to the young.

13. How do animals reproduce?
Oviparous animals (卵生動物)
Testicle
Ovary
A cock 公雞mates with a hen.
The sperm of the cock combines with the hen’s ovum.
The hen lays fertilised eggs. 產下受精卵

14. How do animals reproduce?
The chicken hatches out. 出生
The embryo grows into a chicken 小雞
The embryo胚胎gets nutrients營養from the egg.

15. Can you list more oviparous animals 卵生動物 ?
Butterfly 蝴蝶
Fish 魚

16. Can you list more oviparous animals 卵生動物 ?
Snake 蛇
The fertilised egg of oviparous animal develops inside / outside
the mother’s body.

17. Changing in form 形態 Growth of moths 蛾的生長過程 Fertilised eggs Larva 幼蟲
Mating
After mating, the male’s sperm combines with the female’s ovum to form a fertilised egg.
Adult 成蟲
Pupa 蛹
There are 4 stages in the life cycle of a moth. The form has completely changed. This is called “complete metamorphosis”.完全變態

18. Changing in form Growth of Frogs 蛙的生長過程 Tadpole 蝌蚪 Mating
Tadpoles do not have legs but they have tails.
During mating, the male frog sits on the female’s back. The female frog releases ova into the water, and the male frog releases sperms. The sperms and the eggs combine in the water.
Fertilised eggs
受精卵

19. Front legs are formed
長出前腳
Hind legs are formed
長出後腳
Adult 蛙
Some animals go through big changes when growing up.

20. The life cycle of a mosquito

22. The life cycle of a grasshopper

23. The life cycle of a cockroach

24. Complete metamorphosis Incomplete metamorphosis
完全變態
Incomplete metamorphosis
不完全變態