Unit 4: Reproduction                                                                1   2   3 

2. Reproduction in animals

The life cycle is the joint of stages through undergo an organism during its life,

from it starts as zigote until it becomes an adult able to reproduce.

In an animal’s life cycle it is possible to distinguish several phases during

which the organism changes:

- Fertilisation. The gametes join together to form the zygote.

- Embryonic development. The zygote divides many times to form the embryo.

  This embryo grows and develops until the birth.

- Post-embryonic development. It goes from birth to the acquisition of

  the reproductive maturity. 

  The organism (young) grows and matures to acquire the characteristics

  of the adults.

- Reproduction. The organism produces new individuals. This stage can be

  repeated several times during its life, until it finally dies.

2.1. Identify the phases of the gull’s life cycle. Then listen and relate each description

        with the correspondant phase.