(4 weeks, Paper 2: 54 marks) - hoerskoolbirchleigh.co.za

(4 weeks, Paper 2: 54 marks)

This topic can be divided in the following subsections: 1. Introduction2. Evidence of evolution3. Variation4. Origin of an idea about origins5. Lamarckism6. Darwinism7. Punctuated equilibrium8. Artificial selection9. Formation of new species10. Mechanism of reproductive isolation11. Evolution in present times12. Evidence of common ancestors for living homonids13. Out of Africa hypothesis

2021 1Copyright Hoërskool Birchleigh - Mrs A Laas

Evolution

Concepts

(EG p 15,

TB p 291 - 300,

WB p 2 - 3)

● 1. Introduction

- Biological evolution

- Hypothesis vs Theory

- Theory of evolution

● 2. Evidence for

evolution

- Fossil records

- Biogeography

- Modification of

descent

- Genetics

3. Variation

(EG p 15,

TB p317 - 318,

WB p 4 - 5)

● Species

● Population

● Contribution to

variation

- Meiosis

- Mutations

- Random fertilisation

- Random mating

● Continuous and

discontinuous variation

Evolution theories

(EG p 16,

TB p 302 - 303,

310 - 315,

WB p 7 - 13)

● 4. Origin of an idea about origins

● 5. Lamarckism

- “Law” of use and disuse

- “Law” of inheritance of acquired characteristics

- Reasons for rejection

● 6. Darwinism

- Natural selection

● 7. Punctuated equilibrium

Different species

(EG p16-17,

TB p 306 - 308,

320 - 333,

WB p 13 - 18)

● 8. Artificial selection

- Domesticated animal species

- Crop species

● 9. Formation of new species

- Biological species

- Extinction

- Speciation

- Speciation through geographic isolation

● 10. Mechanism of reproductive isolation

● 11. Evolution in present times

Human evolution

(EG p17,

TB p 341 - 363,

WB p 19 - 33)

● 12. Evidence of common ancestors for living hominids, including humans

- Phylogenetic tree of Hominidae

- Shared characteristics

- Anatomical differences between African apes and humans

- Evidence of common ancestors

● 13. Out of Africa hypothesis

- Evidence of hypothesis

- Timeline for existence of different species of genus Homo

-Interpretation of phylogenetic tree2021 2Copyright Hoërskool Birchleigh - Mrs A Laas

1. Introduction

•Evolution•the proses by which things that exist today arose from organisms that existed in the past.

•Biological evolution•the process where present-day life forms have risen form the past and

•how living things have undergone various changes over long periods of time

•to resemble their present forms that we see today.


•Hypothesis

•a suggested explanation or statement for an observation based on little or no evidence.

• It is the starting point for further investigation

•would be disproved or approved after the investigation and research.

•Theory

•an explanation for an observation that is supported by a large amount of evidence.


•Theory of evolution

•mainly about how life changed after its origin

•regarded as a scientific theory

•since various hypotheses relating to evolution have been tested and verified over time.


2. Evidence of evolution

•Fossils

• Indicate the time frame that the organisms existed

•Transitional fossils show steps in the stages of the development of modern structures.


•Types of fossils

▪ Mineralisation


•Moulds and casts


• Impressions


•Trace fossils


•Natural preservatives


•Biogeography

•the study of the past and present distribution of individual species.

• Similarities in structure of animals in different parts of the world suggest that they evolved from the same common ancestor in the same area.

(refer to continental drift)


•Modification by decent•Organisms living today descended from earlier ancestors

• who were modified, or physically changed•through the course of their decent•Homologous structures support this evidenceo have the same basic plano even though they are different in appearance

of perform different functions.2021 17Copyright Hoërskool Birchleigh - Mrs A Laas

•Genetics

•recorded genetic changes in living organisms over many generations are the main source of evidence that scientists have for evolution

•The identical structure of DNA, identical protein synthesis and other biochemical similarities strengthen the idea that all living organisms have a common ancestor.



Complete Self-Activity 1 on page 3 and 4 of the Grade 12 Life Sciences Workbook.

3. Variation

•Biological species

o group of organisms that can interbreed and produce fertile offspring.

o The offspring in turn can interbreed and produce viable offspring

•Population

o number of individuals of the same species living in a definite/same area at the same time

o The members of a population interbreed with each other.


3. Variation


Variation within populations and species are brought about by various factors. The following factors contribute to variation among individuals of the same species:

•Meiosiso Crossing over▪ Each gamete has an equal chance of receiving either allele of

the homologous chromosome pair.

▪ Provides an opportunity for millions of genetic combinations in gametes.

o Random arrangement of chromosomes▪ Increases the chances of genetic variation

▪ as segments of the chromosome cross over at the chiasmata

▪ resulting in a variety of offspring.2021 23Copyright Hoërskool Birchleigh - Mrs A Laas

• Mutationso Involve the change in the nucleotide sequence of a gene.

o introduce new genes to the make-up of the species

o altered genotype will result in a different of altered phenotype

• Random fertilisationo Meiosis ensures that the gametes produced are not identical

o male and female gametes are brought together randomly which results in a fertilised zygote

o Sexual reproduction allows greater variation in the young

• Random matingo The selection of mates by chance

o promotes genetic variation

o prevents interbreeding


Within a species, variations among individuals are due to continuous or discontinuous variation• Continues variation

o Characteristics where there is a range of inter-mediate phenotypes

o often significantly affected by the environmental influenceso E.g. the amount of milk produced by cows is not only

determined by their genes, but also by the environmental factors such as the quality of the grass that they feed on.

• Discontinuous variationo Characteristics controlled by alleles of a single gene or small

number of geneso The environment has little effect on this type of variationo E.g. blood groups.


4. Origin of an idea about origins

Lamarck (1744 – 1829)

Darwin (1809 – 1882)

Eldredge & Gould (1972)2021 27Copyright Hoërskool Birchleigh - Mrs A Laas

5. Lamarckism

•Lamarck (1744 – 1829) believed that evolution was mostly due to the inheritance of acquired characteristics as organisms adapted to their environments.


•Lamarck used two “Laws” to explain evolution:o “Law” of use and disuse

› If a characteristic is used more and more by an organism during its lifetime it becomes bigger and stronger.

› Characteristic that is not used disappears.

› Creatures can develop new organs or change the structure and function of existing ones as a result of their use and disuse.

o “Law” of the inheritance of acquired characteristics› Organism uses a body part in such a way that it is altered

during its lifetime

› New acquired characteristics could pass on to their offspring

› E.g. Giraffes evolved their necks as each generation stretched further to reach the leaves


5. Lamarckism


•Reasons for rejection of Lamarck’s theories

oOrganisms do not evolve because they wanted to change, changes took place randomly as a result of mutations.

oAcquired characteristics cannot be inherited, meaning that the phenotype cannot affect the genotype as discovered later by Mendel


6. Darwinism

• Darwin’s (1809 – 1882) theory of natural selection suggest that:

o individuals with physical, behavioural or other attributes well-suited to their environments at the time

o are more likely to survive than those less suited

• Darwin’s principles of natural selection can be explained as follows:


6. Darwinism• Darwin’s principles of natural selection can be

explained as follows:o In a population more offspring are born than can surviveo The offspring show a great deal of variation.o There is competition for resources, which is sometimes

called the struggle for survival.o Of the large number of offspring – only a few survive.o Some individuals in the population have a better chance of

survival than others and produce more offspring .o Reproductively successful individuals in the population will

pass their traits, including the favourable traits to their offspring.

o In this way the favourable traits become more common in the population, and over many generations the population evolves.2021 35Copyright Hoërskool Birchleigh - Mrs A Laas

6. Darwinism


Lamarckism Darwinism

Variation only in individuals due to

alterations within their lifetimeVariation within species’ offspring

Changes in a population were

brought about by individuals who

wanted to change

Changes in a population were

brought about randomly due to

environmental factors at the time

Change was brought about by

voluntary adaptation to the

environment

Change was brought about by

natural selection

Individuals within population

changePopulation change

Altered characteristics passed on

to the offspring

Favourable characteristics

inherited through generations that

survived the environment2021 39Copyright Hoërskool Birchleigh - Mrs A Laas

7. Punctuated Equilibrium

•Based on the explanations of Lamarckism and Darwinism 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 the many transitional fossils in the fossil record which show the progressive change over time.


•Fossil records with many gaps does not always show Darwin’s model of gradualism

• Which is a slow, gradual change in species

•Fossil records with many gaps reflects the rapid, sudden appearances of various new species between long periods

•Eldredge and Gould (1972) proposed a theory that explains the long periods in fossil records where species remained unchanged.

• Which is a slow, gradual change in species2021 42Copyright Hoërskool Birchleigh - Mrs A Laas

• Punctuated Equilibrium

o Each gamete has an equal chance of receiving either allele of the homologous chromosome pair.

o Evolution involves long periods of time where species do not change or change very little - known as equilibrium.

o This alternates with (is punctuated by) short periods of time where rapid changes occur.

o As a result, new species are formed in a short period of time, relative to the long periods of no/little change.

o This is supported by the absence of transitional fossils (usually termed ‘missing links’) indicating the period of rapid change.


6. Darwinism


8. Artificial selection

•Also known as selective breeding or unnatural selection

•Deliberate breeding of plants and animals for desired characteristics

•Will not necessarily benefit the survival of the offspring.

•Humans select desired characteristics and therefore serve as the environmental trigger.


•Humans select desired characteristics and therefore serve as the environmental trigger.

• Domesticated animal

o Goats are bred with indigenous goats that can withstand heat and drought and with good meat production. They are also resistant to many diseases

• Crop species

o Maize plants with drought tolerant crossed with maize plants that are diseases resistance. New plant drought tolerant and disease resistance


2021 48


Copyright Hoërskool Birchleigh - Mrs A Laas

2021 49



2021 50



2021 51



2021 52




Complete Self-Activity 4 on page 13 to 15 of the Grade 12 Life Sciences Workbook.

9. Formation of new species

• Extinction is a process by which all individuals of a particular species die out so that not even a single one exists.

• Lead to a loss of biodiversity.

• Speciation is the formation of a new species.

• Lead to an increase of biodiversity.

• Speciation through geographic isolation (Allopatric speciation)


Allopatric speciation


• Speciation through geographic isolation (Allopatric speciation)o If a population of a single species becomes separated by a

geographical barrier (sea, river, mountain, lake)

o The population splits into two populations

o There is now no gene flow between the two populations.

o Each population may be exposed to different environmental conditions / the selection pressure may be different

o Natural selection occurs independently in each of the two populations

o The individuals of the two populations become very different from each other (genotypically and phenotypically)

o Even if the two populations were to mix again, they will not be able to interbreed.

o The two populations are now different species.2021 56Copyright Hoërskool Birchleigh - Mrs A Laas

You must be able to explain allotropic speciation based on different examples given to you in a test

or exam.

Possible examples where you need to apply your knowledge of allopatric speciation are:

• Galapagos finches

• Galapagos tortoises

• Plants on different land masses (linked to continental drift)o Baobabs in Africa and Madagascar

o Proteas in South Africa and Australia

• Any example of mammals on different land masses2021 57Copyright Hoërskool Birchleigh - Mrs A Laas


• Galapagos finches

E.g. How to answer speciation in Galapagos finches

• A common ancestor of all the finches was one species.

• There was variation in the shape of the beaks.

• Birds on different islands experienced different environmental conditions.

• If the birds had more favourable characteristics for that island they survived.

• The gene for the favourable characteristics is passed on and eventually the whole population will have those characteristics.2021 59Copyright Hoërskool Birchleigh - Mrs A Laas

9. Formation of new species


• Galapagos tortoises

10.Mechanism of reproductive isolation


10.Mechanism of reproductive isolation

• Reproductive isolation keeps species separate.

• As populations change in response to the environment of geographic isolation, the changing species may become reproductively isolated from one another.

• Reproductive isolation is the prevention of gene flow between two populations of the same species even if they are able to mix with each other.


• Mechanisms of reproductive isolation

• Each species may have its own courtship displays of its own colouration that is recognised by potential mates.

• They may have different breeding season so that members of different species do not have the opportunity to interbreed.

• The offspring of two species trying to interbreed may be infertile.

• Plants may be adapted to different pollinators.


Any of the mechanism can lead to

speciation!


Complete Self-Activity 5 on page 17 of the Grade 12 Life Sciences Workbook.


Complete Self-Activity 6 on page 18 of the Grade 12 Life Sciences Workbook.

No Marking Guideline will be provided, this section is self-study

11.Evolution in present times

• Increased beak sizes and body in Galapagos finches

•Drug-resistant strains of TB-causing bacteria

• Insects become resistant to insecticides DDT

•Resistance of HIV to anti-retrovirals


12. Evidence of common ancestors for living hominids, including humans

Kingdom: Animalia

Class: Mammalia

Order: Primates


12. Evidence of common ancestors for living hominids, including humans


• Humans are primates.

• All primates share a common ancestor from the distant past.

• Have some characteristics in common.

• As new species evolved, changes in body structure or anatomy occurred new characteristics develop.


• There is evidence that prove the theory of human evolution:

• Fossil evidence key features:

o Bipedalism

o Brain size

o Dentition

o Cranial ridges and brow ridges

• Cultural evidence key features:

o Tool making


Similarities between humans and African Apes• Position of eyes

▪ Forward facing▪ Binocular vision – improves depth perception for climbing

trees

• Limbs▪ Forelimbs modified into arms with hands▪ Hind limbs end in feet▪ Joints in arms allow free rotation of arms for climbing

• Hands▪ Opposable thumbs – able to grip▪ Bare fingertips – nails instead of claws

• Tail▪ No tail


Differences between humans and African Apes


African Apes Humans

Type of

movement

Quadrupedal – generally walks on all

four legsBipedal – walks on two legs

Pelvic girdle Long, narrow pelvis Wide, bowl-shaped pelvis

Position of skullForamen magnum opens towards rear

of skull

Foramen magnum opens centrally

under skull

Face

Protruding (prognathous) jaw

Sloping forehead

Heavy brow ridges

Jaw does not protrude

Face flat

No brow ridges

Teeth and palateLarge canine teeth

Teeth less regular in size and shape

Small canine teeth

Teeth less regular in size and shape

CraniumSmall cranium

Small brain

Larger cranium

Larger brain

•Hands

▪ Opposable thumbs –able to grip

▪ Bare fingertips – nails instead of claws

•Tail

▪ No tail


•Lines of evidence for living hominids including humans

•Fossil evidence

• Thousands of fossils have been found that tell us about changes that occurred.

• Key features of hominid fossils include bipedalism, dentition, palate shape, brain size, prognathism, cranial and brow ridges

• Evolutionary trends provided by anatomical features of fossils


• ArdipithecusAge: live approximately 4.4 mya

Fossil site: North-East Ethiopia

Discovered by Tim White

Characteristics:

▪ Cranial capacity: 300-350 cm3

▪ Cranial and brow ridges: Brow ridges smaller than African Apes

▪ Foramen magnum: further forward than apes

▪ Teeth and palate: Large ape-like teeth with reduced canines

▪ Prognathism: Protruded less than modern apes

▪ Pelvic girdle: rounded upper pelvis and long lower pelvis

▪ Feet: opposable big toe with no arches

▪ Movement: Quadruple in trees, could walk short distances on two legs


2021 81

•Ardipithecus


2021 82

• AustralopithecusAge: live approximately 4 – 2.1 mya

Fossil sites: Ethiopia, Kenya, Tanzania, Taung (Sterkfontein), Malape Cave (Cradle of humankind)

Discovered by Donald Johanson, Raymond Dart & Lee Burger Characteristics:

▪ Cranial capacity: 400-550 cm3

▪ Cranial and brow ridges: Large brow and cranial ridges

▪ Foramen magnum: further forward than Ardipithecus

▪ Teeth and palate: Canines and incisors are smaller and molars larger than earlier hominids, wider palate

▪ Prognathism: present

▪ Pelvic girdle: pelvis broad and quite short

▪ Movement: Quadruple in trees, bipedal on ground


2021 83

•Australopithecus


2021 84

• HomoAge: live approximately 2.1 mya –present

Fossil sites: Tanzania, Java in Indonesai, Swartkrans, Makapangsgat (Limpopo), Border Cave (KZN), Blombos Cave (Western Cape)

Discovered by Louis and Mary Leakey,Eugene Dubois & Tim White

Characteristics:

▪ Cranial capacity: 700-1 600 cm3

▪ Cranial and brow ridges: Large brow and cranial ridges in early species, absent in modern humans

▪ Foramen magnum: Centrally placed at base of skull

▪ Teeth and palate: small regularly shaped teeth, wide palate

▪ Prognathism: absent

▪ Pelvic girdle: pelvis wide, hollow and rounded.

▪ Movement: Bipedal


2021 85

•Homo


•Genetic evidence• Thousands of fossils have been found that tell us about

changes that occurred.

• Comparing mitochondrial DNA (mtDNA) of living hominids attempts can be made to determine when evolutionary pats separated

• Many differences = separation occurred earlier (more time for mutations)

• Fewer differences = separation occurred more recently

• Scientists determined that common ancestors for all living hominids may have existed 15 mya

• Evolutionary paths of humans and chimpanzees separated about 6 mya


•Cultural evidence

• Comparing mitochondrial DNA (mtDNA) of living hominids attempts can be made to determine when evolutionary pats separated

• Production and used of tools and other cultural practices

• Tool making

o Associated with increased intelligence and well-developed hands

o Part of brain responsible for coordination much larger in humans

o Apes use variety of tools but does not make tools

o Most tools made of stone, but other materials have been used2021 88Copyright Hoërskool Birchleigh - Mrs A Laas

13.Out of Africa hypothesis

•Modern humans originated in Africa and then migrated out of Africa to other continents


Supporting this hypothesis:

• Genetic links▪Homonins split from other homonids about 6 mya

▪Developed alongside each other

▪Happened in Africa as modern chimpanzee is purely African species

▪Humans have 98 % genome in common with that chimp

• Oldest fossil Australopithecus/Homo habilis bipedal organism found in Africa

• Analysis of mtDNA show oldest female ancestros of humans are from Africa

• Mutations of Y-chromosomes show oldest male ancestor are from Africa

• Much of this evidence comes from the Rif Valley2021 92Copyright Hoërskool Birchleigh - Mrs A Laas

Lucy


• Homo heidelbergensis


“Karabo”


“Little Foot”



END OF TOPIC 9

(4 weeks, Paper 2: 54 marks) - hoerskoolbirchleigh.co.za

Documents

Transcript of (4 weeks, Paper 2: 54 marks) - hoerskoolbirchleigh.co.za