Reproduction - Weebly › uploads › 2 › 4 › 0 › 6 › ... · Types of Sexual Reproduction • Internal fertilization is the fertilization of the egg by the sperm within the

ReproductionAsexual and Sexual

Junior Science

Introduction

• Reproduction is one of the seven characteristics of living things.

• Reproduction is necessary to ensure the survival of a species.

• All living things reproduce to produce offspring

• Reproduction can occur by two methods

- Asexual Reproduction

- Sexual Reproduction

Modes of Reproduction

In asexual reproduction the genetic make up of the offspring is identical to

the parent.

Sexual reproduction occurs with the fusion of two specialised cells called GAMETES. The

Off spring are not identical to parents.

Asexual Reproduction • In asexual reproduction the genetic make up of the

offspring is identical to the parent. • Asexual reproduction takes place in both plant and animals

Vegetative Reproduction

Part of the plant becomes detached and develops into a new individual.

Budding

An out growth called a bud forms on the parent, it breaks off and develops as a separate organism.

Asexual Reproduction – Animals?

Budding(HYDRA)

An out growth called a bud forms on the parent, it breaks off and develops as a separate organism.

Parthnogenesis (WASPS. APHIDS, REPTILES)

the development of an egg that has not been fertilised into an individual.

Framentation(FLAT WORMS)

the body of the parent breaks into distinct pieces, each of which can produce an offspring.

Sexual Reproduction

• Sexual reproduction occurs with the fusion of two specialised cells called GAMETES.

- A new human live begins when a Sperm Cell (male gamete) fuses with a egg cell (female gamete).

• The fusion of the female and male gamete is called FERTILISATION.

• The new cell formed is called the ZYGOTE

• Through repeated cell division the zygote develops into an EMBRYO

7B New life - How does a new life start?

When an egg and sperm meet, the two nuclei fuse together to form a new living thing.

This process is called fertilisation.

Sexual ReproductionIn most animals, a new life begins when a female egg cell (Ovum) joins with a male sperm cell.

Types of Sexual Reproduction

• Internal fertilization is the fertilization of the egg by the sperm within the body of one of the parents, usually by means of sexual intercourses.

• Internal fertilization usually takes place within the female body, after the male implants sperm.

• However there are exceptionally rare examples, such as seahorses (Sygnathidae), where the female implants her eggs into the male and the zygote is formed within the male’s body.

Types of Sexual Reproduction

• External fertilization occurs when a sperm cell and an egg cell join outside of the body.

• Most amphibians and fish and many invertebrates use external fertilization, producing anything from hundreds to billions of gametes at a time.

• The quick release of gametes into aquatic environments this is called spawning.

• Sometimes females will lay eggs on a particular substrate which are subsequently fertilized by males.

number of eggs

fertilisation

time until birth

care after birth?

survival of offspring

1000s 2-8 3-5 1

external internal internal internal

5-15 days 3 weeks 8-9 weeks 9 months

no yes yes yes

low high high high

7B New life – Reproductive patterns

Animals reproduce in different ways to ensure survival depending on their environment.

Compare the reproductive patterns of different animals.

Sexual Reproduction

Asexual Reproduction • Advantages of asexual preproduction

– Animals that remain in one particular place and are unable to look for mates can produce offspring.

– Numerous offspring can be produced without "costing" the parent a great amount of energy or time.

• Disadvantages of asexual reproduction

– is the lack of genetic variation. All of the organisms are genetically identical and therefore share the same weaknesses.

– If the stable environment changes, the consequences could be deadly to all of the individuals.

Sexual Reproduction • Advantages of sexual preproduction

– Give rise to unique individuals

– Promotes survival.

– Removes bad genes from a population.

• Disadvantages of sexual reproduction

– Required two parents

– Requires a lot of time and energy

– Can prevent favourable genes from being not passed on.

– Produces fewer offspring than asexual reproduction