1. Methods for Determining Phylogenetic Relationships

2. REVIEW:
Similarities and differences in DNA base sequences or amino acid sequences can be compared to determine evolutionary relationships.
TODAY:
Comparison of DNA sequences has led to new information about plants.
DNA can also be compared through hybridisation.

3. Plant Classification
Upon germination, the cotyledon may become the embryonic first leaves of a seedling.
Species with one cotyledon are called monocotyledonous ("monocots"). Plants with two embryonic leaves are termed dicotyledonous ("dicots").

4. Flowering plants are classified into two groups:
Monocotyledonous plants 1 cotyledon strap like leaves parallel veins flower parts divisible by 3 example: kaffir lily

5. Flowering plants are classified into two groups:
Dicotyledonous plants 2 cotyledons broad leaves branching veins flower parts divisible by 4 or 5

6. Comparing monocotyledons and dicotyledons:
Feature
monocotyledon
dicotyledon
Number of cotyledons 1 2
Leaf shape
strap like
broad
Vein pattern
parallel
branching
Flower parts divisible by: 3
4 or 5
Example
Kaffir lily
Hibiscus

7. Which plant is a monocotyledon and which is a dicotyledon?B

8. Which plant is a monocotyledon and which is a dicotyledon?

9. BUT…
This assumes that all plants with similar structures share a common ancestry.
From animals, we know this might not be true…

10. Types of classification
Artificial classification:
Divides organisms by physical characteristics, such as size or number of legs.
Describes by the same function, not the same evolutionary origin.
What are the problems with this?

11. So, DNA sequences were analysed…
Read the article and answer these questions:
How were plants originally classified?
How would these plants have been grouped originally?
3. Why is it important to understand about the evolution of plants?

12. DNA Comparisons Base sequences of particular genes are compared.
In plants, this was genes for proteins involved in photosynthesis and other essential (and common!) functions.
What genes might be analysed in animals?

13. DNA Hybridisation
Closely related species have similar DNA base sequences.
DNA strands can be separated by exposure to high temperatures.

14. DNA Hybridisation
Mixing single stranded DNA from different species will allow hybrid DNA to form.
The higher the temperature needed to separate the hybrid DNA, the more complementary bases were joined and the more closely related the species.

15. DNA Hybridisation

16. Comparing Proteins

17. Comparing Proteins

18. Comparing Proteins Most closely related: Donkey/human Cat/human
Cat/dog
Dog/human
Duck/pigeon
Then:
Cat/donkey
Dog/donkey
Mammals/birds

19. Let’s draw an evolutionary tree
Now try the cytochrome C question.

22. What’s left?

23. What’s left?

24. Easter Holidays Get your Unit 2 booklet up to date
Catch up on lessons you’ve missed
Identify topics you need help with
Do some (more) revision:
Notes
Cards
Test yourself
Past papers etc.