5.2.2 Continuity of Species

Question 1

Continuity of Species

Answer 1

The ongoing survival of species as a result of characteristics being passed from parents to offspring in a continuous lineage.

The inheritance of characteristics from ancestors relies on the passing on of consistently accurate genetic information (genetic stability) and the occasional introduction of variation so that species can adapt and survive in a changing environment.

Both genetic stability and variation are essential to the contnuity of species.

Question 2

Genetic Continuity Depends On…

Answer 2

1. Mitosis must result in two daughter cells with identical genes as the original cell.
2. During sexual reproduction of organisms, the offspring must have the same number of genes as the parent organism and variations must be non-lethal/detrimental.

Question 3

Genetic Continuity

Answer 3

• Consistent replication prior to cell division (mitosis, meiosis)
• Orderly distribution of chromosomes when cells divide and when gametes form
• Fertilisation methods that ensure that individuals of the same species breed successfully
• Methods to ensure embryo survival
• Natural selection so that ‘survival of the fittest’ occurs

Question 4

Genetic Variation

Answer 4

• Mutation - changes in DNA, either spontaneously or by mutagen
• Mixing of parental genes during sexual reproduction (crossing over, independent assortment, random fertilisation), allowing offspring to differ from their parents and each other