Upload
imelda
View
217
Download
1
Embed Size (px)
Citation preview
8/14/2019 6.2 Causes of Variation
1/14
6.2 Causes of Variation
8/14/2019 6.2 Causes of Variation
2/14
Causes of variation
Two main factors:
1. Genetic factors
2. Environmental factors
8/14/2019 6.2 Causes of Variation
3/14
1. Genetic factors
Influenced by crossing-over,
independent assortment, mutation and
random fertilisation
8/14/2019 6.2 Causes of Variation
4/14
8/14/2019 6.2 Causes of Variation
5/14
8/14/2019 6.2 Causes of Variation
6/14
Crossing over, independent assortment and fertilisation.
8/14/2019 6.2 Causes of Variation
7/14
Genetic variation caused
by mutation Mutation sudden permanent change in the
nucleotide sequence of the DNA or in theamount of DNA.
Two types:1. Gene mutation
2. Chromosome mutation
Mutation can cause by:
1. Chemical or physical agents (mutagens)2. Mistakes that occur during DNA replication
3. Uneven distribution of the chromosomes duringcell division
8/14/2019 6.2 Causes of Variation
8/14
8/14/2019 6.2 Causes of Variation
9/14
8/14/2019 6.2 Causes of Variation
10/14
2. Environmental factors
Caused by surrounding condition such as:1.Water
2.Sunlight
3.Nutrients
4.pH
5.Temperature
The effect depends on how much condition
received by an organism during growth
8/14/2019 6.2 Causes of Variation
11/14
E.g.
- Chinese primrose (Primula sinensis) willproduce white flower when grow in a
warm temperature and will produce red
flower when grow in cool temperature.
8/14/2019 6.2 Causes of Variation
12/14
Environmentally induced cannot be
passed to offspring but genetic variationcan be inherited
Some variation in characteristics results
from interaction between genetic and
environmental factors
E.g. the action of sunlight on genes for
lighted-coloured skin may result in
darker skin
8/14/2019 6.2 Causes of Variation
13/14
What are the importanceof variation in the survival
of a species? Provides the necessary adaptations
for the species to compete and
survive. Essential for survival of the species.
8/14/2019 6.2 Causes of Variation
14/14
Exercise
Do Checkpoint 6.2 on page 202 inthe textbook