Transcript Sexual and Asexual Reproduction and Variation

Sexual Reproduction
• Sexual Reproduction is the creation of offspring using
gametes which causes variation.
• Sexual Reproduction involves two organisms. Male and
female gametes (sex cells) join together to create a new
cell. This develops into a new individual. The joining of
gametes is called fertilisation.
• Sexual Reproduction causes variation in the offspring
because of the gametes. They contain half of the genes
from the mother and half from the father. The offspring
look a bit like each parent but not identical to them.
Variety is important because if a species where all the
same, a disease could cause the species to die out.
Advantages and Disadvantages of
Sexual Reproduction
Advantages
• Variety
• Reduces the chance of offspring inheriting a genetic
disease
• Leads to continuous evolution
Disadvantages
• There is the chance of not finding a mate
• Sexually transmitted diseases can be easily contracted
• There is no guarantee that offspring will be born
Examples of Sexual Reproduction
• Humans, animals
Gametes
Gametes have half of the normal number of chromosomes.
E.g.. The human body cell has 46 chromosomes but human
gametes have 23. Fertilisation produces a new cell with the
normal number of chromosomes- in the case of humans 46.
Chromosomes are found in the nucleus of a cell. They contain
a lot of genes. The different genes control the development of
different characteristics in an organism. A gene is a section of
DNA (deoxyribose nucleic acid) that carries the code for a
particular protein.
In humans and most animals, the female gametes are the eggs
and the male gametes are the sperm.
Asexual Reproduction
• Asexual Reproduction involves only one organism
and the offspring are exact clones of the parent.
• There is no variety in offspring from asexual
reproduction because the offspring inherits all of
the genes from the one parent, which means it is
a natural clone.
• The differences between a daffodils sexually and
asexually produced offspring is the sexually
produced offspring contains half the genes of
each parent, where as the asexually produced
offspring contains all of one parents genes.
Advantages and Disadvantages of
Asexual Reproduction
Advantages
• More efficient way of passing on genes
• Don’t need to waste energy looking for a mate
Disadvantages
• Negative characteristics will be passed on
• All offspring are the same- no variation
• There isn’t a chance of evolution
Examples of Asexual Reproduction
• Potatoe Plants, Daffodils, Spider Plant
(Chlorophytum)