Reproduction in complex life

OUR ANIMAL REPRODUCTION:

Reproduction is the ability of all living things to create other beings similar or identical to them.

Our animal has sexual reproduction because two individuals produce sexual cells or gametes. The union of male and female gamete forms a cell, the zygote, which develops into a new being.

This type of reproduction has:

- advantages: increases diversity because descendants are not identical to either of their parents but they have characteristics of each of them.

- disadvantages: the parents must come together to reproduce and that is not always easy.

Animals can display or not sexual dimorphism. This means that some species, in addition to having different reproductive organs, males and females are very different in their physical appearance.

Our animal doesn´t display sexual dimorphism because the two sexes differ only in their sexual organs.

Cellular reproduction:

Our animal and our plant have binary fission that means that the mother cell divides into two daughter cells of identical size. In this way our animal and our plant multiply its cells.

SEXUAL REPRODUCTION:

Sexual reproduction in animals involves two parents who have sex organs which produce sex cells called gametes that are produced in the gonads.

 It has several phases:

1.Formation of gametes:

Gametes are formed in the reproductive system, they are composed of:

- sexual organs or gonads: produce sexual cells or gametes.

                        ● the male gonads: testicles:

                        - produce the male gametes or spermatozoa

                        ●the female gonads: ovaries:

                        - produce the female gametes or ova.

2. Fertilisation:

Fertilisation can be internal or external in animals.

Our animal has internal fertilization that takes place inside the female reproductive system through copulation.

3. Development of the zygote:

It takes place in two stages:

●Embryonic development: occurs from the time the zygote is formed until a new being is born.

Our animal is a viviparous animal that means that animals develop inside the mother’s uterus, feeding from her through an organ, the placenta, which connects the embryo to the mother. When it is fully developed, the new individual comes out of the mother’s body, this is called a birth.

●Post-embryonic development: begins when the individual is born and it ends when it becomes an adult.

In our animal this is a direct development because the new born individual is similar to the adult, only smaller. It consist of the growth and maturity of the organs.

OUR PLANT REPRODUCTION:

Plants can be clasified in:

Our plant carries out sexual reproduction because two individuals  carry out it. They produce gametes, and the union of a male and females gamete forms a cell, the zygote, which develops into a new being.

SEXUAL REPRODUCTION IN PLANTS WITH SEEDS: there are five stages in this process:

●The formation of gametes: the flower

The flower is a structure made up of modified leaves that contains the reproductive organs of the plant where gametes are produced.

The parts of the flower are:

-the calyx (outer whorl): it is made up of small green leaves called sepals which protect the internal organs

-the corolla (the next whorl): it is made up of coloured leaves called petals which attract animals for pollination.

-the androecium: the male reproductive organ: it consists of the stamens: a stamen has a filament and a wider part called an anther where pollen grains develop. Male gametes form inside the pollen grains.

-the ginoecium or pistil: the female reproductive organ: it consist of a bottle shaped organ which has three parts:

                        - the ovary (where the females gamete is produced)

                        - the style

                        - the stigma

●Pollination:

It is the transfer of pollen grains from the anthers to the stigma of the pistil of the same flower (self-pollination) or of another flower of the same species (cross-pollination).
Our plant has self-pollination.

There are two types of pollination, anemogamous and entomogamus.
Our plant has entomogamous pollination because pollen grains are transported from flower to flower by insects. Because of this, our plant has attractive flowers and produces sweet substances (nectar) to attract insects. Therefore, it does not need to produce much pollen.

●Fertilisation:

It consists of the union of the male gamete with the females gamete.

The phases are:

-           The pollen grains reaches the flower’s stigma (pollination) and it forms a pollen tube that grows along the style until it reaches the ovary

-           The male gamete goes inside its pollen tube to the ovary where the female gamete is

-           The male and female gametes join through the process of fertilization and the zygote is formed.

●The formation of the seed and the fruit:

*the seed: it is formed when the zygote develops.

It has three parts:

-           The embryo which is produced when the zygote develops and it is a tiny version of the future plant. It has three part: the radical (small root), the hypocotyl (small stem) and one or two leaves called cotyledons that store nutrients.

-           Endosperm is a nutritious substance that envelops and feeds the embryo.

-           The seed coat envelops the seed and protects it. 

*the fruit: it is formed around the seed in angiosperms: after fertilization, the flower loses the sepals, petals, stamens, the style and the stigma. The walls of the ovary get fatter and form the fruit with the seed inside.

Its function is to protect the seed and help in its dispersion.

Our plant has fleshy fruits which store nutrients.

●Dispersion and germination of seeds:

The seed or fruit can be dispersed by the wind, by animals,….in order to colonise new places..

The germination takes place if the environmental conditions are favourable when the seed falls to the ground.

Germination has several phases:

-           The seed absorbs water which produces that its coat to break

-           The seed opens

-           The embryo begins to develop creating a new plant

-           The new plant feeds on the supplies stored in the seed (when it can’t carry out photosynthesis)

-           When it can carry out photosynthesis it begins to make its own nutrients.