Evolution answers to grade 12 Activities

2. 1.1 Biological evolution
1.2 The theory of recapitulation
1.3 Radiometric dating
2.The THEORY OF EVOLUTION includes the following:
All present day life forms descended from and are related to those
that lived in the past.
Present day life forms may look different from those of the past as
they have become modified from one generation to the next.

3. Homologous Structure
Similar structures in various organisms that are due to a common
ancestor. They may be used for different purposes e.g. The forearm of a
lizard (walking), dolphin (swimming) and a bat (flying) have the same
anatomy but are use for different forms of locomotion.
Analogous Structure
Organisms have similar structures but there is no common ancestor.
These structures have similar characteristics that perform the similar
functions, e.g. spines on an Echidna and cactus.
lizard dolphin bat

4. 4. Ideas from fossil record
Earth is 4.5 billion years old.
First life forms 3.8 million years ago.
Today’s life forms are more complex.
Many life forms are extinct.
Fossils show gradual increase in size to present day forms.

5. 5.
• Biochemical molecules DNA, ATP
• Gene similarities. Some portions of DNA with no function.
• DNA triplet code the same in protein synthesis.
• Same 20 amino acids
• Cellular respiration pathways are the same

6. Activity 2
1. The original finch population had flown in from South America’s
mainland. There were no natural predators for these birds and their
numbers increased.
This lead to competition amongst the birds.
2. There was no competition so the numbers of birds increased.
More birds lead to competition for food.
3. To the forest.
4. Moved to the thicker forest that was inland.
5. Less competition

7. 6.The birds in the forest only mated with those that lived in
the forest.
7
•Within a large population there was variation
•Some birds had large beaks some shorter ones. Then
there was a selection pressure. Those with short
beaks mover to an area where the food was plentiful.
•The populations separate.
•Those which are adapted to the new environment
survive and pass these genes on to future generations.

8. The Law of Use and
Disuse
If organs were used
they would
increase in size or
efficiency.
If organs were not
used they would get
smaller and
disappear.

9. Eyes of moles have stopped functioning because of
disuse.

10. Legs of snakes have been reduced due to disuse.

11. Webbed feet in birds are the result of
spreading the toe bones and the skin
between them in order to swim to find food
and escape predators.

12. The Law of Inheritance of Modified
Characteristics.
The physical changes acquired by
parents during their lifetime could be
passed on to their offspring.

14. Explanation of the long legs and necks in giraffe using
Darwinian Evolution

15. Differences between Lamarck and
Darwin’s Theory
Darwin Lamarck
1
Genetic change is random;
adaptive changes arise by
chance, before any need for
them arises. The
environment selects the
best-adapted individuals
from the population.
1
Genetic change occurs in
response to need; ie the
environment causes
adaptations to develop.
2
Changes in the body
(somatic changes) acquired
during the life are not
handed on to the offspring.
2
Adjustments resulting from
sustained use of the body are
handed on to the offspring.

17. ACTIVITY 3
Darwin’s Natural Selection Worksheet
Read the following situations below and identify the 5 points of Darwin’s natural
selection. There are 2 types of worms: worms that eat at night (nocturnal) and
worms that eat during the day (diurnal). The birds eat during the day and seem to
be eating ONLY the diurnal worms. The nocturnal worms are in their burrows
during this time. Each spring when the worms reproduce, they have about 500
babies but only 100 of these 500 ever become old enough to reproduce.
a. What worm would be naturally selected for?
Darwin's 5 points: Identify the 5 points in the scenario above.
Population has variations.
_________________________________________________________________
Some variations are favorable.
_________________________________________________________________
More offspring are produced than survive
_________________________________________________________________
Those that survive have favorable traits.
_________________________________________________________________
A population will change over time.
_________________________________________________________________
Some worms eat at night and some eat during the day.
Nocturnal worms
Nocturnal worms were not eaten.
Of the 500 offspring produced 100 survived.
The diurnal worms were being eaten so wouldn’t reproduce, only the nocturnal worms reproduced.
Eventually only nocturnal worms would survive.

18. There are 3 types of polar bears: ones with thick coats, ones with thin
coats and ones with medium coats. It is fall, soon to be winter. The
temperatures are dropping rapidly and the bears must be kept warm,
or they will freeze to death. Many of the bears have had ~2 cubs each
but due to the extreme temperatures, many mothers only have one
cub left.
a. What bear will be naturally selected for?
__________________________________
Darwin's 5 points: Identify the 5 points in the scenario above.
Population has variations.
______________________________________________________________
Some variations are favorable.
______________________________________________________________
More offspring are produced than survive
._____________________________________________________________
Those that survive have favorable traits.
_____________________________________________________________
A population will change over time.
______________________________________________________________
Bears with thick coats.
Bears with thick coats, thin coats and medium coats.
Bears with thick coats.
Mothers have 2 cubs only one survives.
Bears with thick coats.
Only bears with thick coats will survive.

19. In ostriches, there are 2 types: ones that run fast and those that run slowly. The
fast birds can reach up to 40 miles an hour. Jackals love to eat ostrich, and they
can reach speeds of up to 35-40 miles per hour. A flock of ostrich will lay 10 eggs
(each mother only lays 1),but many rodents break into the eggs and eat the
foetus before they hatch.
a. What ostrich will be naturally selected for?
Darwin's 5 points: Identify the 5 points in the scenario above.
Population has variations.
__________________________________________________________________
Some variations are favorable.
__________________________________________________________________
More offspring are produced than survive.
__________________________________________________________________
Those that survive have favorable traits.
__________________________________________________________________
A population will change over time.
__________________________________________________________________
Ostriches that are fast and look after their eggs.
Ostriches that are fast and slow and some look after their eggs, whilst others don’t.
Ostriches that are fast can run away from jackals and baby ostriches will hatch.
Many eggs are laid (10) many of which are eaten.
Ostriches that are fast and look after their eggs.
All ostriches will be fast and look after their eggs.

20. Activity 10.2 pg. 201
1.1 HMS Beagle
1.2 Galapagos Islands
1.3 finches
2.1 D
2.2 B
2.3 A

21. 3. Organisms evolved in response to the environment; not because
they wanted to.
Little evidence to support that acquired characteristics are
passed on go future generations.
4

22. Within a population there is a of offspring produced.
The offspring are from each other: the offspring shows
Off spring for resource and or something happens, a drought, fire, which
acts as a causing organisms to compete for limited resources.
Those organisms with the genetic traits that allow them to will and will pass
the traits on to future generations.
Those with the “undesirable” traits will die and will not pass these traits on to future
generations. The undesirable traits will be lost to the population.
We say those that have survived have been for.

26. Speciation

27. Allopatric Speciation of the Galapagos tortoises

29. Treatment
for MDR TB
has more
side effects
than TB.

30. Activity 6 (Isaacs pg. 211 10.8)
1.1 fossils
1.2 species
1.3 population
1.4 finches
1.5 natural selection
1.6 allopatric speciation
1.7 homologous structures
1.8 analogous structures

31. 2.1 Natural Selection
2.2
• Within a population, there is a large number of offspring.
• Individuals within the population show genetic variation. Some are
tall and some are short.
• The tall individuals are able to eat the high hanging fruit and survive.
• The reach adulthood and pass their “tall” genes on to future
generation.
• The short individuals starve and die. They do not pass their “short”
genes on to future generation.
• Eventually only tall individuals will be present in the population.

32. 3.1 Some tortoises have rounded shells and some have flattened
shells.
3.2 The tortoises from Hood Island.
3.3 Those from Pinta Island.
3.4 These tortoises have more or less the same shaped shell, so they
will be able to go to the same burrows etc. as the Hood Island
tortoises. Also they have the second longest neck so they will be
able to reach up to the same vegetation as the Hood Island
tortoise.

33. 4.1.1 The population consisted of more susceptible mosquitoes
compared to the few resistant mosquitoes.
4.1.2 Only the resistant mosquitoes survived.
4.2 Equal numbers of resistant and susceptible mosquitoes survived.
The susceptible mosquitoes did not out number the resistant
mosquitoes.
4.3 There are more mosquitoes after the second pesticide
application because there were more resistant mosquitoes in the
population prior to being treated.
4.4 They were not able to survive the pesticide application. They
were unable to produce offspring to pass that gene on to future
generations.

34. Natural Selection
• Within a population, there is a large number of offspring.
• Individuals within the population show genetic variation. Some are
resistant to pesticide and some are not resistant and are susceptible.
• The resistant individuals are able survive the pesticide application and
survive.
• They reach adulthood and pass their “resistant” genes on to future
generation.
• The susceptible individuals die. They do not pass their “susceptible”
genes on to future generation.
• Eventually only resistant individuals will be present in the population.

35. 5.
One of the observations Darwin made during his study
of pigeons was about artificial selection. In 1859
Darwin and Wallace jointly proposed that new species
could develop by the process of natural selection.
Using an example each, describe natural and artificial
selection and also highlight the differences between
these two processes.