EDCC 515
Assignment: 2
School subject: LIFE SCIENCES
Grade: 12
Main topic: EVOLUTION
Sub-topic: EVOLUTION BY NATURAL SELECTION
Term: 3
Name: VINCENT N.E. YENIKA
Student number: 36237604
Email: vincentyenika@yahoo.com
Cell phone number: 0797924883
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Index:
1. Checklist
3
2. Summary of learning content for learners with references
4
3. Class activity
a. Investigation activity to introduce natural selection
b. Case study to introduce speciation
19
4. Homework activity (with memorandum)
a. Ideas of evolution and natural selection
b. Speciation
21
5. Formal assessment
a. Test
b. Memorandum / Marking guideline
25
6. References
34
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1. Checklist
Yes
Did you use the NWU title- and index page?
Did you update the details on the cover page?
Did you update the page numbers on the index page?
Did you replace the question marks on the index page?
Did you complete the summary of the content as explained?
Did you include TWO “active” class activities?
Did you include TWO homework activities with memorandums?
Will the homework activities keep the learners busy for the desired time?
Did you complete a summative assessment/test with memorandum?
Does the test count 50 marks?
Did you include the various levels of questions according to Bloom’s
taxonomy?
Did you include a reference list according to the NWU referencing
guidelines?
Did you proofread your assignment, and did you use Arial 12?
Did you safe the PDF document correctly, eg. 12345678 Assignment 2?
Are you satisfied with your effort?
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No
SUMMARY OF CONTENT
OBJECTIVE/OUTCOMES
Upon completion of this chapter, learners should be able to:
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Understand the Origin of ideas about origins
Identify and explain the evidences for evolution
Explain the sources of variation
Understand and explain the theories of evolution
Explain how Lamarckism could explain evolution
Explain Darwin’s theory of evolution by natural selection
Explain how does natural selection work?
Explain the theory of Punctuated equilibrium
Compare and contrast Lamarckism vs Darwinism
State the Generic account of speciation
Explain the Formation of a new species (Speciation) by Geographical barriers
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Using example discuss Artificial selection in plants and animals
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Differentiate between natural selection and artificial selection
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Identify and explain the mechanisms for reproductive isolation
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Explain practical examples of Evolution in present times using Resistance to antibiotics in
TB
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ORIGIN OF IDEAS ABOUT ORIGINS
The theory of evolution has been developed over many years by many different scientists and
is regarded as a scientific theory since various hypotheses relating to evolution have been
tested and verified over time.
DEFINITION:
Evolution is the process by which new types of organisms develop from other existing types
of organism.
BIOLOGICAL EVOLUTION
It is a special type of evolution that refers to changes that living things have undergone
over long period of time
WHY IS THE THEORY OF EVOLUTION REFERRED TO AS “MODIFICATION WITH
DESCENT”?
All present-day life forms have descended from and are related to, those that lived in the
past.
All present-day life forms may look different from those that they descended from because
they became modified from one generation to another.
What is a THEORY
A well-substantiated explanation of some aspect of the natural world that can incorporate
facts, laws, inferences, and tested hypotheses.
Example: The sun is the Centre of the universe, around which all the planets revolve
(Heliocentric theory)
What is a HYPOTHESIS
A testable statement about the natural world that can be used to build more complex
inferences and explanations.
Example: The high incidence of HIV-AIDS is due to the lack of education about the causes
of the disease
WHY IS EVOLUTION A THEORY
Evolution is regarded as a scientific theory since various hypotheses relating to evolution
have been tested and verified over time
EVIDENCE OF EVOLUTION
Assumption made by scientists in presenting these evidences
The assumption is that species changes through the forces of natural selection acting on the
great genetic variation within species.
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Fossils
covered in Grade 10
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Different fossils are found in different rock layers with
the oldest fossils in the oldest rock layers with transitional
fossils present.
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This systematic change through time is termed
descent with modification.
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The evidence shows characteristics that make
organisms similar to one another largely from the study
of fossils
Geologist are scientists who study the structure of the earth. They
can date rocks by studying the chemical elements in them.
Palaeontology is the study of fossils
The fossil records provides a history of past life on earth, and that
life began as a single-celled bacteria about 3.6 billion years ago
The fossil record also show us how living organisms have changed
and develop over time.
When scientist study fossil records, they look for similarities and
differences in the type, origin and functions of body structures.
This provide clues about the relationship that exist between extinct
fossils species and extant species that are still living today
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Biogeography covered in Grade 10
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Genetics
Biogeography is the study of where species are found
and why they are found there.
There are many different collections of plants and
animals in regions of the same line of latitude, with
similar climates and conditions, suggesting such
organisms have a shared ancestor.
Biogeography refers to the study of past and present distribution of
individual species.
This studies shows that closely related species tend to be found in
the same geographic location, whereas very similar habitats (the
same ecological niches) in distant regions are occupied by very
different species
new concept for Grade 12 – see below
Species that are closely related have a greater genetic similarity to
each other than distant species and therefore share a more recent
common ancestor.
Homologous
structures
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Homologous structures are characteristics that are shared by related
organisms because they have inherited them from a common ancestor.
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the fore limb of all animals arose from that of a common
ancestor in which the fore limbs had the same basic plan
these structures now show variations (differences) because they
became modified to perform different functions
this is referred to as divergent evolution (homologous
structures are evidence of divergent evolution)
the way characteristics in organisms’ changes over time is
called modification by descent
scientists interpret the presence of homologous structures to
mean that all species which show common ancestor which
became adapted to live in different environment. This is called
adaptive radiation
adaptive radiation usually occurs when environmental changes
cause numerous extinction, and the surviving species start to
occupy the ‘new’ ecological niches created
Genetic evidence and variation
These evidences come from DNA structure, the sequences of genes and proteins, identical
protein synthesis and similar metabolic pathways.
The structures or processes in the field of genetics and molecular biology as evidence are:
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Identical DNA structure
Similar sequence of gene
Similar portion of DNA with no function
Identical protein synthesis and similar proteins
Similar respiratory pathways
VARIATION
This refers to small differences that exist between individuals of the same species or
population. E.g. difference in height or eye colour.
CAUSES OF GENETIC VARIATION
 MUTATION
o Mutation involve a sudden change to the structure of a gene.
o This leads to an altered genotype resulting in a different or altered phenotype.
 MEIOSIS
o CROSSING OVER
 During prophase 1 of meiosis, there is an exchange of chromatid
segments between homologous chromosomes.
 When meiosis is complete, new combination of genetic material
results in the gametes,
 Making them different from each other
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o
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RANDOM ASSORTMENT OF CHROMOSOMES
 The chromosomes arrange themselves randomly at the equator
during metaphase 1 and metaphase 2.
 As a result, during anaphase 1 and anaphase 2, the chromosomes or
chromatids may move to the poles in different combinations
 Leading to gametes that differ from each other
CHANCES OF FERTILISATION
o Firstly, the egg cells and the sperm cells produced by meiosis are different
from each other.
o Since there is random fertilisation of these different gametes, there will be
different combination of genetic material in the offspring
RANDOM MATING
o Random mating of individuals and successful fertilisation occurs in a
population,
o The variety of gene combinations formed is even greater.
o This lead to even more variation within a species
THEORIES OF EVOLUTION
Erasmus Darwin (1731 – 1802)
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Ideas on evolution that were proposed by Erasmus Darwin:
o All life developed from simple forms.
o There are similarities amongst various organisms
o Artificial selection and metamorphosis showed how changes may have
occurred
Jean Baptiste de Lamarck (1744 – 1829):
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Two ideas of Lamarck in explaining evolution:
o Use and disuse
o Inheritance of modified characteristics
Alfred Wallace (1823 – 1913)
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Natural selection as an explanation for evolution
Charles Darwin (1809 – 1882)
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Charles Darwin's Theory of Evolution by Natural Selection
Jean Baptiste de Lamarck
Explain the two "laws" of De Lamarck
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Law of use and disuse
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Law of inheritance of acquired characteristics
Explain examples of the application of de Lamarck’s theory (such as in the long neck of
giraffe or the legs of snake)
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The most significant advocates of the idea that species are not static, but have changed over
time, were Jean Baptiste de Lamarck and Charles Darwin. Of these, Charles Darwin is best
known, particularly as a result of his famous book called “The Origin of Species”.
LAMARCKISM
Jean-Baptiste Lamarck
https://www.bbvaopenmind.com/en/science/leading-figures/what-remains-of-lamarck/
LAMARCK THEORIES
 Use and disuse of organs
Changes in the environment create new needs that cause organisms to
modify their existing organs to meet the need. Repeated use of the organ
would cause it to enlarge and become more efficient. Disuse of an organ
would cause it to degenerate
 Inheritance of acquired characteristics
The modification an organism acquired during its life time could be pass on to its
offspring.
How did Lamarck explain the long necks of giraffe?
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Elongation of a giraffe’s neck over time according to Lamarck
Source: http://faculty.washington.edu/sr320/?p=2004
Why Lamarck was wrong
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There is no evidence that Acquired characteristics can be inherited/do not
cause any change to the DNA of an organism's gametes (sperms or ova)
Organisms did not evolve because they want to evolve
Lamarck believed in determinism (internal drive of organisms to change)
For this reason, Lamarckism is not accepted today as an explanation for evolutionary
change. His work did, however, set the groundwork for scientists like Charles Darwin.
Darwin’s theory of evolution by natural selection
Charles Darwin’s theory of evolution by natural selection is one of the basic concepts for
understanding evolution and is based on the four main observations made by him while on
his around-the-world trip on the ship, the HMS Beagle.
DARWIN’S THEORY OF NATURAL SELECTION
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Most species produce a large number of offspring in their life-times
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Variation: Offspring of the same species show a great deal of variation
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Competition: These offspring compete with each other for food, shelter etc
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Survival: Only a small number of offspring survive
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Genetics: Organisms pass Genetic traits on to their offspring.
later used the term survival of the fittest
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Natural selection: Those organisms with the Most Beneficial Traits are more likely to
Survive and Reproduce. Natural Selection from generation to generation caused the
population to gradually change …
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leading to the evolution of new species
Charles Darwin
Source: https://www.biography.com/news/charles-darwin-facts-darwin-day
Based on his observations, Darwin came to three main conclusions:
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All organisms are involved in a struggle for survival and only those best
suited to the environment would survive there.
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Organisms that survive are more likely to reproduce, and therefore pass on
their useful characteristics to their offspring.
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Over many generations, reproduction between individuals with different
genetic makeup changes the overall genetic composition of the population.
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How does natural selection work?
A generic explanation of natural selection is given in Table below
1
There is a lot of variation among offspring as offspring differ from their parents (due
to crossing over, random arrangement of chromosomes, etc.).
2
When the environment changes or there is competition (for food, space, etc.).
3
The offspring with characteristics or traits that make them better suited to the new
environment or competition will be most likely to survive and reproduce.
4
The organisms without the desired characteristic or trait are less able to survive in
the new environment or competition and so will die out.
5
This means that more offspring in the next generation will have the advantageous
characteristic(s). The next generation will have a higher proportion of individuals with
the new trait or characteristic.
6
These differences accumulate and eventually all individuals in a population have the
new trait or characteristic.
THE THEORY OF PUNCTUATED EQUILIBRIUM (by Niles Eldredge and Stephen Jay
Gould)
Based on Darwinism, it is thought that evolution takes place through an accumulation of
small or gradual changes that occur over a long period of time.
This is supported by many transitional fossils in the fossil record which shows the
progressive changes over time.
Punctuated equilibrium explains the speed at which evolution takes place, as follows:
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According to the punctuated equilibrium, evolution is not gradual as proposed by
Darwinism.
Evolution involves long periods of time where species do not change or change very
little (known as equilibrium). due to stable environment
This alternate with (is punctuated by) short period of time where rapid changes
occurs through natural selection. Due to unstable environment
As a result, new species are formed in a short period of time, relative to the long
period of no/little change.
This is supported by the absence of transitional fossils (usually termed missing
links) indicating the period of rapid change.
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Illustration of punctuated equilibrium
Source: https://www.saburchill.com/IBbiology/chapters05/017.html
Figure 4: Punctuated equilibrium (Gould) versus gradualism (Darwin)
When a new species branched off from a parent species, changes occurred quickly, but
thereafter, the organism changed very little.
In a fast-changing environment, species needed to change rapidly to adapt to the
environment, failing which, they would become extinct.
Lamarckism vs Darwinism
The table below outlines the differences between Lamarckism and Darwinism.
Lamarckism
make-up of a
population
transformation of a
species/population
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members of population are all
the same
Darwinism
members have similar
characteristics with a measure
of variation
populations, not individuals,
individuals are able to transform transform over time and only
during a life time
through genetic means
mechanism of
change
individual chooses which
traits to pass on to offspring
natural
selection
–
the
environment exercises selective
pressure causing change
changes are directed to meet
survival
variation exists regardless of
organisms needs.
NATURAL SELECTION AND FORMATION OF NEW SPECIES
Species: a group of organisms that are similar in appearance, share the same DNA
Speciation: is the evolutionary process by which new biological species arise, due to the
splitting of the lineage. Speciation by natural selection may be allopatric or sympatric
Every population has some sort of genetic variation and these variations are important as
they increase a species chance of surviving in a changing environment (natural selection).
Geographic speciation is one-way speciation occurs.
GEOGRAPHIC SPECIATION
Geographic speciation occurs when part of a population becomes isolated from the parent
population due to physical barriers. Such barriers could be continental drift, oceans, rivers,
mountains, or other natural disturbances such as volcanos or earthquakes.
The images below show how two new species can arise as a result of being separated,
over a long period of time, due to a geographic barrier.
GENERIC ACCOUNT OF ALLOPATRIC SPECIATION
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E.g. when a population is geographically isolated from other populations, gene flow
stops.
Within each of the two groups there is variation
Each group undergoes natural selection (different selection pressures)
as a result of varying environmental conditions-and develops differently genotypically
and phenotypically
since the geographical barrier prevents gene flow/reproduction between the two
populations
The differences that develop between the two populations prevent them from interbreeding even if they were to mix (reproductive isolation mechanisms)
such that one or both of the groups becomes a new species
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ILLUSTRATION OF ALLOPATRIC SPECIATION
Source: https://www.storyboardthat.com/storyboards/zacheryevans/allopatric-speciation
Artificial selection
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Artificial selection is the deliberate breeding of plants and animals for desired
characteristics that would not necessarily benefit the survival of the descendants.
Humans select the desirable characteristics and therefore serve as the
environmental trigger.
EXAMPLE IN ANIMALS:
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By selecting cows which produce large amounts of milk and whose mothers and
grand-mothers were also high milk producers,
And allowing them to mate with bulls whose mothers and grand-mothers were also
high milk producers,
Cow which produce high milk than their ancestors, have been developed.
EXAMPLE IN PLANT
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By deliberate selection of polyploidy plants, bigger plants of watermelon have been
produced
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SIMILIARITIES BETWEEN ARTIFICIAL AND NATURAL SELECTION
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Variation occurs in the specific population
Variation in the population is hereditary
The outcome is the same, that is, the population change over time and certain
characteristics become more common.
DIFFERENCES BETWEEN NATURAL AND ARTIFICIAL SELECTION
Natural selection
The environment or nature is the selective
force
Artificial selection
Humans represent the selective force
Selection is in response to suitability to the Selection is in response to satisfying
environment
human needs
Occurs within a species
May involve one or more species (as in
cross breeding)
Mechanisms for reproductive isolation
Sympatric speciation (no geographic):
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This is the genetic divergence of various populations from a single parent species,
which leads to the creation of new species.
It results when Reproductive isolation occurs by either preventing fertilisation or by
creating a degenerate or sterile hybrid.
There is no geographical isolation like with Allopatric speciation.
Reproductive isolation result because of:
o BREEDING AT DIFFERENT TIMES OF THE YEAR:
 When the time of mating activity of 2 species occurs at different times
of the year,
 May prevent contact with closely related species and
 Reduces chances of mating and reproducing new offspring
 E.g. butterfly
o Species-specific courtship behaviour:
 Many animals have specific behaviour patterns that attract the
opposite sex like calls, rituals,
 That prevent mating with other organisms
 Example: birds will sing
o Adaptation to different pollinators:
 Flowers of many angiosperms are adapted to promote pollination by
only one species or group of species of insects or
 Other pollinators that prevent cross breeding
 And hence keep the species separate
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o
o
 Example: plant like the rose flower
Infertile offspring
 If two species mate and produce a hybrid offspring,
 The species are reproductively isolated if hybrids are sterile
 Example: a horse and a donkey produce a mule
Prevention of fertilisation:
 The sperm from one species cannot fertilise the eggs of another
species
 Sperm of one species might not be able to survive the condition in the
reproductive structure of a female of another species
 Or it might be chemical factors that prevent the sperm from
penetrating the membrane of the egg of another species.
Evolution in present times
Evolution is always happening. Most of the time it is impossible to observe changes in
populations and species because evolution happens very slowly – thus the theory of
gradualism. However, there are some cases (e.g.: rapidly producing organisms such as
viruses and bacteria) that allow scientists to study how species change in response to
environmental factors. Pathogens (viruses and bacteria) evolve quickly because there is lots
of natural variation amongst them and the fact that mutations occur most often in rapidly
reproducing organisms.
Resistance to antibiotics in TB
Development of resistant strains of tuberculosis-causing bacteria (MDR and XDR) to
antibiotics
As a result of their rapid generation times, changes in bacterial populations can show significant
evolutionary changes in relative short periods of time. Some evolutionary changes in bacteria,
such as the acquisition of antibiotic resistance can be a threat to human health. Antibiotics are
drugs that fight bacterial infections. After their discovery in the 1940s, they transformed medical
care and dramatically reduced illness and death from infectious bacterial diseases. However
some bacteria have developed antibiotic resistance. Resistance infections inhibit the treatment of
patients and increase patient mortality (death). The cumulative effect of antimicrobial resistance
costs millions of rands every year.
Tuberculosis (TB) is a chronic bacterial infection caused by the bacterium Mycobacterium
tuberculosis. Unfortunately, the incidence of this disease keeps increasing in South Africa.
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The evolution of drug resistance in bacteria
Bacterium with
Susceptible
bacteria
Slightly
insensitive
bacteria
Within any
population, there is
genetic variation. In
this case the
susceptibility is with
some bacteria more
than others
greater resistance
survive and multiply
The amount of
antibiotics taken is
too low, or the full
course of antibiotics
is not completed
and only the most
susceptible bacteria
die, while some
survive
Now a population of
insensitive bacteria has
developed. Within this
population there is also
variation, in the susceptibility
to antibiotics. As treatment
continues, some bacteria may
acquire grater resistance
Drug resistant genes
can be transferred to
non- resistant
strainsBacterium with
A Highly resistance
population has evolved.
The resistance bacteria
can exchange genetic
material with other
bacteria, passing on the
resistance genes. The
antibiotic used will now
be ineffective.
Adapted from: https://ib.bioninja.com.au/standard-level/topic-5-evolution-and-biodi/52natural-selection/antibiotic-resistance.html
TERMINOLOGY
biological evolution
any genetic change in a population that is inherited over several
generations
biological species
a group of organisms with similar characteristics that interbreed
with one another to produce fertile offspring
population
a group of individuals of the same species occupying a
particular habitat
punctuated
equilibrium
evolution characterised by long periods of little or no change
followed by short periods of rapid change
natural selection
mechanism of evolution - organisms survive if they have
characteristics that make them suited to the environment
artificial selection
human-driven selective force, e.g. breeding of plants and
animals to produce desirable traits
speciation
the formation of a new species
geographic
speciation
formation of a new species when the parent population
separated by a geographical barrier
reproductive isolation
a mechanism that prevents two species from mating with one
another and making fertile hybrids
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CLASS ACTIVITY 1
This investigation is to be done in class before teaching natural selection
Aim: to show that organisms that are best adapted in their environment survive
Requirement:
2 green coloured A4 papers (like the butterfly product range)
2 yellow coloured A4 paper
A puncher
A forcep
Procedure:
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Take one of the green coloured A4 paper and using a puncher, create about 30 holes
on them.
Collects the circles of paper that will be in the puncher
Repeat the same procedure for the yellow paper
One the green paper (acting as background) place 15 green circles and 15 yellow
circles
Do the same for the yellow paper (acting as background).
A learner will be given 45 seconds to use a forcep take out as many circle as he can
see on the yellow paper background.
The same procedure is repeated for the green paper background.
The procedure is repeated with about 6 learners
Observation:
More yellow circle was picked-up in the green background and more green circle were
picked up in the yellow background.
Inference:
The teacher will now explain that because circles that are similar to the background could
camouflage and therefor were not easily seen by the learners. The circle are the organisms,
the background their environment and the leaners are predators. Organisms that are best
adapted will survive.
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Class activity 2
This case study is to be done in class before teaching speciation through geographic
barrier.
Leaners will have to read this and the teacher will ask them some questions like
1. Do you think they were pretending?
2. Do you think even if they were to recognise each other they will want to get married?
JOHN AND MARY
John and Mary were born in a small informal settlement in Marikana north-west Province
in South Africa. John was 3 years older than mary. They were very good friends and
were always sharing their dreams. They use to play together, swim in the dirty nearby
stream together and were always seen with each other. They did not even have proper
clothings and could not even use cutlery to eat.
SOURCE: https://www.news.uct.ac.za/article/-201612-09-integrating-informal-settlements
When John was 13 years old, his long lost uncle who travelled
to Egoli (Johanesburg) before John was even born return home. He took john back with
him to Gauteng were they live in an up market suburb in sandton. Sent John to a
Multiracial school and after 14 years, John was now a successful engineer.
SOURCE:
https://www.property24.com/articles/south-africas10-most-expensive-suburbs-revealed/26025
The company he worked for sent him on a mission to supervise a
project in Marikana. When he went there, he met with mary and they could not even
recognise each other.
WHAT DO YOU THINK HAPPENED?
(story by Vincent yenika: HOD CPC and std: NWU)
I will then explain to the class that, you can see that before they were together and happy.
After they were separated, they all live under different condition and adapt differently. When
they were brought to together, they could not recognise each other. They behave like
different species
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Homework 1
Question 1
1.1. What type of characteristics does nature select during evolution?
(1)
1.2 In nature, there is always a fight for survival due to competition, predation and adverse
weather conditions. Suggest a collective term for all these factors
(1)
1.3 Why is the concept of natural selection so important?
(2)
1.4 Why is natural selection not a random process?
(2)
1.5 In a population of mice, half were light in colour and half were dark.
a)
If an owl, hunts in the area at night, which mice have the more
favourable characteristic? Explain your answer in terms of natural
selection.
(3)
b)
If the predator was a snake that detects the body heat of its prey,
which mice would probably have the more favourable variation? Explain your
answer.
(3)
Question 2
The graph below shows the speed at which evolution occurs in a species of butterfly.
B
A
time
2.1.
Explain the trend in evolution represented by:
a)
phase A
(2)
b)
phase B
(2)
2.2.
In view of the trend represented by A and B, what type of evolution is
represented by the graph?
2.3.
Explain why the chances of speciation are great during phase B.
(1)
(2)
(7)
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Memorandum on home work 1
1.1 those that benefits the organism✓
1.2 selective forces or forces of natural selection✓
1.3 It provides a mechanism for evolution ✓, explaining that animals are able to change
to a changing environment and that these small changes over time can result in a
new species being formed ✓ that is different to ancestral species.
1.4 The environment actively selects ✓ which organisms are best suited to their
environment ✓. The ways by which variation arises in a population may be random
but natural selection is a very selective process.
1.5
a. The dark coloured mice ✓ – they will be difficult to spot in the dark ✓ as they
will be well camouflaged at night ✓ in their surroundings
c)
The
light coloured mice ✓ – lighter colours absorb less heat than darker colours ✓ .
Darker coloured mice will absorb more heat and therefore will be more “visible” to
the snake ✓ .
Question 2
2.1. a) No evolutionary change takes place in phase A ✓ – the species is in equilibrium with
its environment ✓.
b) Phase B points to an accelerated evolutionary change ✓ due to rapid environmental
changes ✓.
2. 2. Punctuated equilibrium ✓
2.3. During phase B, species with advantageous characteristics, i.e. suitable to the new
environment, survive and reproduce. ✓ Species that do not have advantageous
characteristics die out. Thus the chances of speciation during phase B are much greater
than during phase A ✓.
(7)
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HOME WORK 2
Question 1
1.
Bontebok are antelope that are found in the Western Cape. Two main
populations exist, one at the Bontebok National Park and the other at Table
Mountain National Park. These two national parks are hundreds of kilometres
apart. Scientists believe that due to geographical separation, speciation may
occur.
1.1
Define the term “speciation”.
(2)
1.2
Define the term ‘species’.
(3)
1.3
Name the type of speciation that may occur in the bontebok
populations.
(2)
Question 2
Darwin discovered two different species of tortoises on two different island in the
Galapagos. One had a domed shell and short neck, the other had an elongated shell and a
longer neck. The two islands had very different vegetation. One of the islands (island X)
was rather barren, dry and arid. It had no grass but rather short tree-like cactus plants. On
the other island (island Y), there were no cactus plants but it had a good supply of water
and grass grew freely. The diagram below shows the two main
species
of tortoise.
Tortoise 1
Tortoise 2
2.1 Which tortoise (1 or 2) would have been found on:
2.2.
2.3.
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a)
Island X
(1)
b)
Island Y
(1)
Describe how the two tortoise species became different species.
(5)
Scientists believe that the variation in populations lead to the formation of
new species. List four sources of variation in populations.
(4)
Question 3
3.1.
3.2.
List four ways in which artificial selection has been used in agriculture.
(4)
Copy the table below and complete it showing the differences between artificial
selection and natural selection.
(9)
Artificial selection
Natural Selection
Driven by...
Rate of change...
Amount of variation achieved
End result
3.3. Humans have been domesticating plants for years and today, most agricultural
species come from domesticated varieties.
a)
Define the term “domestication”.
(2)
b)
What was one of the first crops to be domesticated in the world?
(1)
c)
Name two characteristics that were selected for in the domestication
of the crop mentioned in (b) above.
(2).
Homework 2
Question 1
1.1) The process by which new species are formed ✓ ✓
1.2 A group of organisms with similar characteristics ✓ /that are closely related to each other
and are able to interbreed✓ and produce viable/fertile offspring ✓
1.3 Allopatric speciation or geographic speciation ✓ ✓
Question 2
1.1 a) Island X Tortoise 2 ✓
b) Island Y Tortoise 1 ✓
1.2
The ancestral tortoise population was separated by a geographic barrier (the ocean) as they
were found on the mainland and on islands ✓
• There was no gene flow between the populations ✓
• Each population was exposed to different climatic conditions and different vegetation types,
so that natural selection occurs independently in both populations ✓
• The individuals in the populations become very different to each other both in their genes
(genotypically) and their appearance (phenotypically) ✓
• Even if the populations were to mix again, they will not be able to reproduce with one
another ✓, since they are now two different species.
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1.3 crossing over during Prophase I of meiosis ✓; the random arrangement of maternal and
paternal chromosomes ✓; random fertilisation of egg cells ✓; random mating ✓
Question 3
3.1.
• produce disease resistant crops
• improve crop yield
• adapt old crops to grow in adverse conditions
• increase shelf life
•enhance nutritional value and flavour of crops
3.2
Artificial selection
Natural Selection
Driven by...
man
nature
Rate of change...
faster
slower
Amount of variation achieved
less
more
End result
Improve crops and
livestock for human
consumption
Suitable to the
changing environment
3.3
a) The selecting and breeding of organisms ✓ with desirable characteristics ✓
b) maize (Zea mays) ✓
c) Any two:
reduced covering of the seed ✓ ; retention of seeds (kernels) on the cob ✓ ; erect habit with
a single stalk ✓ ; larger ear structure ✓
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SUMMATIVE ASSESSMENT
Section A
Question 1
1.1
Various options are provided as possible answers to the following questions.
Choose the correct answer and write the letter (A – D) next to the question number
(1.1.1–1.1.5) for example 1.1.6 D.
1.1.1
The theory that describes the speed at which evolution took place……..
A
B
C
D
1.1.2
gradualism
punctuated equilibrium
Jean Baptiste de Lamarck
Charles Darwin
The reason that Lamarck would have provided for the long beak of the
hummingbird is that:
A
all hummingbirds have the same beak length
B
there is natural variation in beak length and some birds are
therefore better suited to feed on nectar
C
D
1.1.3
the more the hummingbird used its beak, the longer it grew
hummingbirds with shorter beaks were more fit for survival
Lamarck's 'laws' of use and disuse and inheritance of acquired
characteristics were:
A
rejected, because only characteristics that benefit offspring
can be inherited.
B
not rejected, because evidence shows that acquired
characteristics can be inherited
C
rejected, because only characteristics that are coded for in the
DNA can be inherited
D
not rejected, because Darwin's theory supports Lamarck's
(3 x 2) = (6)
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1.2
Give the correct biological term for each of the following descriptions. Write only the
term next to the question number.
1.2.1
A tentative explanation of a phenomenon that can be tested.
1.2.2
The distribution of species in different parts of the world.
1.2.3
Variation that results in distinct phenotypes.
1.2.4
The breeding of plants and animals to produce desirable
characteristics.
1.2.5
The process whereby organisms better suited to their
environment survive and produce more offspring.
(5 x 1) = (5)
1.3 Indicate whether each of the descriptions in Column I applies to A ONLY, B ONLY,
BOTH A AND B or NONE of the items in Column II. Write A only, B only, both A
and B or none next to the question number.
Column I
1.3.1 The selection and breeding of organisms
desirable characteristics by humans
1.3.2 Example of a reproductive isolating
mechanism
Column II
with
A: natural selection B:
artificial selection
A: breeding at the same time
of the year
B: adaptation to different
pollinators
1.3.4 A group of similar organisms that can interbreed A: species
to produce fertile offspring
B: genus
(3 x 2) = (6)
1.4
Many dog breeds exist today as shown in the diagram below.
(a)
(b)
Explain why all breeds of domestic dogs belong to the same
species.
(2)
Describe how artificial selection has led to different breeds of
domestic dogs.
(3)
(5)
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1.5
This question applies to the diagram on the next page.
The ancestor of the modern horse had very differently shaped foot bones.
Scientists believed that the structure of the foot bones evolved as the environment
changed from swampy areas with soft mud to drier and harder soil. This allowed
the animals to move effectively in each habitat.
ankle bones
foot bones
Eohippus
50
Mesohippus
35
Merychippus
Equus
25
5 - millions of year ago
Key: the shaded bones are the ones that touched the ground
1.5.1. Describe two changes to the bones that have taken place over the
past 50 million years.
(2)
1.5.2. Eohippus lived in swampy areas with soft mud. Explain one
advantage to Eohippus of the arrangement of bones in its feet. (2)
(4)
Section A: [26]
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Section B
Question 2
2.1
Study the diagram below of the moth species that originally belonged to a single
population but was later separated by a mountain into two groups.
Species A
Mountain
range
Species B
Species C
2.1.1
Name and define the process which is illustrated in the diagram
above.
(3)
2.1.2. Explain the importance of the process you identified in question
2.1.1 above.
(2)
2.1.3. Why is species A the ancestor of species B and C?
(2)
(7)
2.2.
Study the extract below which describes the evolution of the snake.
How snakes lost their limbs has long been a mystery to
scientists: New research on a 90-million-year-old snake fossil
suggests that snakes evolved to live and hunt in burrows as many
snakes still do today.
It is generally accepted that snakes and lizards are closely related, although
very few transitional fossils have been found to support this generalisation.
(adapted from https://www.ed.ac.uk/news/2015/snakes-271115)
a)
b)
Explain one characteristic that you would expect a transitional
snake fossil to have.
(1)
Describe how would Jean Baptiste de Lamarck have explained the
loss of limbs in snakes?
(4)
(5)
[12]
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Question 3
3.1
Lizards of a certain species on an island are usually brown in colour. A mutation in
one gene for body colour results in red or black lizards. Black lizards camouflage
well against the dark rocks and warm up faster on cold days which will give them
energy to avoid predators.
Scientists investigated the relationship between the colour of lizards in a population
and their survival rate on an island.
They conducted the investigation as follows:
•
They selected a group of lizards of a certain species in a habitat.
•
They recorded the percentage of each colour (brown, red or black) in
the selected group.
•
They repeated the investigation over a period of 30 generations of
offspring.
The results of the investigation are shown in the table below.
Colour of
lizards
Percentage (%) of each colour In
the population
Initial
population
10th generation
20th
generation
30th
generation
Brown
80
80
70
40
Red
10
0
0
0
Black
10
20
30
60
(adapted from https//hhmi.org/bioInteractive)
3.1.1 State the:
a)
independent variable
b)
dependent variable
(1)
(1)
3.1.2. Use the theory of natural selection to explain the higher percentage of black lizards
in the population of the 30th generation.
(5)
(7)
3.2
The diagram shows the distribution of various camels on the different continents.
The arrows indicate the current distribution of the animals.
llamas
dromedary
bactria
( adapted from http://www.ck12.org)
Explain how speciation of camels may have occurred.
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(5)
[12]
Section A: [26]
Section B: [24]
Total Marks: [50]
Memorandum
Section A:
1.1
1.1.1
B
1.1.2. C
1.1.3. C
1.2
1.2.1
hypothesis
1.2.2. biogeography
1.2.3. discontinuous
1.2.4. artificial selection
1.2.5
natural selection
1.3
1.3.1
A only
1.3.2
B only
1.3.3
A only
1.4
(a).
They are able to interbreed with each other ✓ to produce fertile offspring ✓
(b).
Humans chose characteristics pleasant to humans and bred dogs with those
phenotypes and genotypes ✓ to create dogs that suit their needs, e.g. hunters,
companions, helpers. ✓ The different breeds are bred for the different needs and therefore
selected characteristics. ✓
1.5.
1.5.1. Bones became larger / longer / thicker ✓,
there were fewer bones ✓,
fewer bones touched the ground ✓ (any two)
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1.5.2
Large/r surface / area in contact with the ground ✓ *compulsory
low / less pressure on the ground ✓, less likely to sink into ground
/ mud ✓, could run faster ✓, easier to escape predators ✓
(* compulsory + any one)
SECTION B
2.1.
2.1.1. Speciation
2.1.2. increases diversity of species / biodiversity ✓ as the new species formed are
genetically different
Introduces reproductive isolation mechanisms ✓ and eliminates gene flow between
different populations ✓
Decreases extinction rates of species ✓ as the new species might be able to survive certain
conditions due to its different genetic composition. ✓ (any one X 2)
2.1.3. Species B and C ✓ evolved from species A. ✓
OR
Species A existed prior to species B ✓, and species C evolved at the same time as species
B ✓ (any one x 2)
2.2
(a).
Smaller limbs than the ancestor compared to no limbs of modern snakes ✓ OR
More vertebrae than the ancestor but less than the modern snake ✓ (any one)
(b).
Lizards crawled into burrows to find food / escape from predators ✓.
They did not use their limbs anymore ✓
The limbs became smaller and eventually disappeared ✓
They passed on this characteristic to their offspring ✓
QUESTION 3
3.1
3.1.1. colour of lizards
3.1.2. rate of survival
3.1.2. There is variation in colour amongst the lizards
* Red and brown lizards have a disadvantageous characteristic / trait and ✓
* are not camouflaged / cannot warm up fast enough to have energy to run away ✓ and are
killed by predators ✓
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* The black lizards have the advantageous trait and ✓
* are better camouflaged / warm up faster to have energy to avoid predators ✓
and survive / reproduce ✓
The allele for black colour is passed on to the next generation to produce more black lizards
in the next generation ✓ (any 2 + * 4 compulsory marks)
3.2.
*The common ancestor / original camel population was separated into different populations
by the sea / due to continental drift ✓
There was no gene flow between the populations. ✓
Each population was exposed to different environmental conditions / selection pressures ✓
Natural selection occurred independently in each of the populations ✓
The individuals of each of the separated populations became different from each other over
time genotypically and phenotypically ✓
Even if the three populations were to mix again they would not be able to interbreed to
produce fertile offspring. ✓
(any 4 + 1* compulsory)
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Bibliography
Bowie, M., de Beer, J.. Khan, M.A.. Naude, F. Pretorius, E.J.P.,Whitlock, C.E., Wiese, S.M.
Via afrika life sciences: grade 12 learners’ book: cape town: Nasou and via afrika
Gebhardt,A., Farhem, B., Preethlall, P., Pillay, S. Study and master life sciences: grade 12
llearner’s book. 3rd ed. Pretoria: BIS
Grogan,J.& Suter, R. Mind action life sciences: grade 12 text & work book. Preoria: Allcopy
publishers
Isaac, T., Chetty, S., Manganye H.T., Mpondwana N.L., White, L. Understanding life
sciences: grade 12 learners’ book. 3rd ed. Dormerton: Pulse
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