Download Evolution

Papers 1 and 2 – Topic 5 – Ecology (Classification and Natural
Selection)
Paper 3 – Option D - Evolution
Paper 1 and 2 – Topic 5
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the process of cumulative change
in the heritable characteristics of a
population
 Jean Baptiste de Lamarck (1744-1829)
 Russel Wallace (1823-1913) and Charles Darwin
(1809-1882)
 A process in nature in which organisms possessing
certain genotypic characteristics that make them
better adjusted to an environment tend to survive,
reproduce, increase in number or frequency, and
therefore, are able to transmit and perpetuate their
essential genotypic qualities to succeeding
generations.
 Fossil Records
 Artificial Selection
 Homologous Structures
 Too many offspring
 over production of offspring leads to intra-species
competition and survival of the individuals best suited to that
particular environment.
 competition can also lead to adaptive behaviours.
 Natural Variation in a Population
 random assortment of chromosomes
 crossing over of segments of chromosomes result in new
combinations of genes, different than the parental
combinations
 random fusion of gametes in sexual reproduction
 additional variations arise due to mutations, either
chromosomal or gene
 The favourable characteristics are expressed in the
phenotypes of some of the offspring
 These offspring may be better able to survive and
reproduce in a particular environment; others will be
less able to compete successfully to survive and
reproduce.
 Examples
 Antibiotic Resistant Bacteria
 Peppered Moth
 Heavy Metal Tolerance in Plants
Paper 3 – Option D
 Biologists believe that organic evolution by natural
selection accounts for the major steps in evolution.
 macroevolution – major developments such as the
origin of the eukaryotic cell, the origin of multicellular
organisms, and the origin of vertebrates from nonvertebrates
 microevolution – the relatively minor changes that
arise and lead to the appearance of new, but closely
related species.
 Theory of evolution - the Big Bang.
 Chemical Reactions to produce simple organic
molecules, from inorganic molecules
 Assembly of the molecules into polymers
 Self Replication of Polymers
 Development of Membranes to enclose the polymer
 Heat, Temperature and Lightning – Miller and Urey
Experiment
 Recreated ancient atmosphere (nitrogen, water vapour
and carbon dioxide, smaller amounts of methane,
ammonia, carbon monoxide, sulphur dioxide, hydrogen
sulphide and hydrogen cyanide.
 Lightning and UV radiation to provide energy
 Other Possibilities
 In Space – Panspermia
 Alternating Wet and Dry Environments
 Near Volcanos
 Deep Sea and Ocean Vents
 As the organic compounds are made, they arrange
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themselves in lines – polymers (Using the Clay Lattice as a
template)
Lines of molecules form early enzymes (ribozymes)
Catalyse reactions, such as peptide bond formation
RNA strand is made and due to enzymes, a complementary
strand can be made, and then copies are made
Longer and longer double stranded pieces are made,
forming , now DNA
DNA more useful as it is longer and can hold more
information (RNA – 1500 nucleotides max)
 Membranes were needed to separate the external
environment from the internal environment
 Phospholipids would have formed and due to
hydophilic and hydrophobic properties, would form
spheres in water (called coacervate)
 Due to the bilayers, an internal environment would
form, and if the early molecules (RNA to DNA) were
trapped in the membrane, protobionts would have
formed
 Early cells were anaerobic and heterotrophs
 As nutrients decreased in amount, some evolved to
become chemoautotrophic, using the gases in the air
 Since there was a large amount of CO2, some early
prokaryotes used the gas, to produce early
carbohydrate. The waste product was O2, which went
into the atmosphere
 The formation of an ozone layer in the upper
atmosphere commenced
 The ozone layer began to reduce the incidence of UV light
reaching the Earth’s surface.
 Terrestrial existence (rather than life restricted to below
the water surface) became a possibility
 Other prokaryotes, simply ‘fed’ on the organic molecules
available in their environment.
 The bacteria had evolved aerobic respiration and so had
the enzymes not only of glycolysis, but also of the Krebs
cycle and terminal oxidation.
Paper 3 – Option D
 Gene Pool – all of the genetic information present in the
reproducing members of a population at a given time
 Allele Frequency – is a measure of the proportion of a
specific variation of a gene in a population.
 The allele frequency is expressed as a proportion or a percent,
and can be calculated by the Hardy-Weinberg equation (more
later).
 For example, it is possible that a certain allele if present in
25% of the chromosomes studied in a population. One
quarter of the loci for that gene are occupied by that allele.
Keep in mind it is not the same as the number of people who
show a particular trait.
 Species
 Morphological Definition
 A type of organism that has fixed characteristics that
distinguish it from all other species
 Biological Definition
 Group of actually or potentially interbreeding
populations, with a common gene pool, which are
reproductively isolated from other such groups
 Speciation
 the evolution of new species, requires that allele
frequencies change with time in populations.
 Mechanisms = Isolation
 Geographic (Allopatric)
 Temporal (Sympatric)
 Behavioral (Sympatric)
 Geographical Isolation (Allopatric)
 Ex. Galapagos Islands
 Ex. Snails
 Lizards
 Temporal (Sympatric)
 Ex. Plants and Apple Maggot Fly
 Behavioral (Sympatric)
 Ex. Konrad Lorenz and the Gwan
 Movie
 Hybrid Infertility
 Adaptive Radiation
 many similar but distinctive species evolve relatively rapidly
from a single species or from a small number of species.
 When the species evolves different ways, this is called
DIVERGENT EVOLUTION
 The new species is different than the first, in terms of
the adaptations that have taken place
 Living organisms often find the same solution to
particular physiological problems, and as a result the
organisms, in response to their environment, can
become morphologically similar, even though they are
not related to a common ancestor.
 This is called CONVERGENT EVOLUTION
 Gradualism
 Punctuated Equilibrium
 Transient Polymorphisms
 When there are two alleles for a gene in the gene pool, it
is called polymorphic.
 If one allele is gradually replacing the other, based
upon environmental pressures, this is called balanced
polymorphism
 Ex. Peppered Moth (Biston betularia)
 Balanced Polymorphism
 When two alleles of a gene can persist indefinitely in the
gene pool of a population
 Ex. Sickle Cell Anemia
 HbN HbN – normal
 Hbn Hbn - Sickle Cell anemic but immune to malaria
 HbN Hbn – heterozygous, slight anemia, but resistant to
malaria
Paper 3 – Option D
 Humans are known as Homo sapiens (modern man).
The full classification is:
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Kingdom:
Phylum:
Subphylum:
Class:
Subclass:
Order:
Suborder:
Family:
Genus:
Species:
Animalia
Chordata
Vertebrata
Mammalia
Eutheria
Primates
Anthropoids
Hominidae
Homo
Sapiens
 Use Fossil Records as evidence
 Use Carbon – 14 Dating to see how old the fossil or
artefact is.
 For C14, the half-life is 5730 years.
 For fossils and rocks older than 60 000 years, we use
K40 dating.
 What defines humans as primates?
 Opposable Thumbs for grasping
 Mobile arms with shoulder joints allowing movement in
three planes and the bones of the shoulder allowing
force to be applied to the arms.
 Stereoscopic vision
 Skull Modified for upright posture – Magnum foramen
 Ardipithecus ramidus
 Lived approximately 5.8 – 4.4 mya in Ethiopia
 Australopithecines
 A. afarensis from the Afar desert (4-2.8 mya)
 A. africanus (3-2 mya) found in South Africa.
 A. robustus (2-1.4 mya) in South Africa.
 A. Africanus
 Homo genus.
 They were from around 2 mya and had larger brains (600 cm3)
and walked upright.
 H. habilis (handy man). thought he arose from A. afarensis 2 mya in
East Africa and used simple tools.
 Homo erectus was from Africa. It is thought it migrated to other parts
of the world and had a larger brain than H. habilis.
 H. neanderthalensis, which lived in Eurasia from 200 000 to 30 000
years ago
 Next was H. sapiens, which came to Europe.
 H. Habilis
 H. Erectus
 H. Neadrathalis
 Hominid Diets and Brain Size
 Australopithecus brains were only slightly larger in
relation to body size than the brains of apes.
 Powerful jaws meant a largely vegetarian diet.
 2.5 mya, Africa became drier, led to an evolution for
survival, as there were less plants
 Tools to hunt, increased supply of protein correspond to
the changes in brain size
 Hominid Diets and Brain Size
 The correlation between the change in diet and the
increases in brain size can be explained in two ways
 1. Eating meat increases the supply of protein, fat and energy
in the diet, making it possible for the growth of larger brains
 2. Catching and killing prey on the savannas is more difficult
than gathering plant foods, so natural selection will have
favoured hominids with larger brains and greater
intelligence.
 Genetic and Cultural Evolution
 In the recent evolution of humans, cultural evolution has
been very important and has been responsible for most of
the changes in the lives of humans over the last few
thousand years.
 This is much too short a period for genetic evolution to
cause much change.
 Some aspects of cultural evolution, ex. Medicine, have
reduced natural selection between different genetic types
and therefore, genetic evolution.
Paper 1 and 2 – Topic 5 - Ecology
 Classification
 The process of classification involves giving every
organism an agreed name and arranging organisms into
groupings of apparently related organisms.
 Scheme of the overall diversity of living things.
 Classification attempts to reflect evolutionary links.
 The Binomial System
 Carolus Linnaeus in the 18th Century
 The first part of the name is the genus or the generic name
based upon a noun.
 The second name is the species, or the specific name, based
upon an adjective.
 Ex. Canis lupis – dog / wolf and grey /brindled coat
 Scheme of Classification
 Kingdom – largest and most inclusive grouping
 Phylum / division – organisms constructed on a similar
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plan
Class – a grouping of orders within a phylum
Order – a group of apparently related families
Family- a group of apparently related genera
Genus - a group of similar and closely related species
Species – a group of organisms capable of interbreeding
to produce fertile offspring
 Kingdoms
 Prokaryotes –Examples are bacteria and cyanobacteria
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 Protista –Examples are Euglena and Paramecium
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 Fungi –Examples are yeasts and mushrooms.
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 Plantae –Examples are mosses, ferns, flowering plants.
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 Animalia - Examples are humans and jellyfish.
 Plantae Phyla
 Bryophytes (mosses, liverworts)
 Filicinophyta (ferns and horsetails)
 Coniferophyta (cedars, junipers, fir, pine trees)
 Angiospermophyta
 Animalia Phyla
 Porifera (sponges)
 Cnidaria (corals, sea anemones, jellyfish, sea jellies, hydra)
 Platyhelminthes (flatworms)
 Annelida (earthworms, leeches and polychaetes)
 Mollusca (snails, clams, and octopi)
 Arthropoda (insects, spiders, scorpions, and crustaceans (crabs,
shrimp))
 Dichotomous Key
Paper 3 – Option D - Evolution
 A mathematical formula to detect change or constancy in gene pools
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The formula
 For 2 alleles of a gene:
 Use B for dominant, and its frequency in the population is p (a number between
0 –1)
 Use b for recessive, and its frequency in the population is q (a number between 0
–1)
 A gene must have an allele, with the options either B or b. No other options are
available, so if B is present, it frequency is 1, and b is 0, therefore p + q = 1 (1+0)
 Each gene has two alleles, so if the frequency of B is p, then BB is p2
 If the frequency of b is q, then bb is q2
 If you have Bb, the frequency is 2pq
 Since genotypes must be one of the three, the percentage in
a population will be:
p2
+
2pq
+
q2 = 1
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 In order to be used, the following conditions need to be
observed.
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Large population
Random mating occurs
No directional selection (no advantage)
No allele specific mortality
No mutations
No immigration or emigration
Paper 3 – Option D - Evolution
 One of the objectives of classification is to represent how
living and extinct organisms are connected, which means
natural classification.
 Phylogeny
 is the study of the evolutionary past of a species.
 Species which are the most similar are most likely to be
closely related
 Species which show a higher degree of difference are
considered less likely to be closely related.
 Values to classifying this way.
 Identify unknown organisms, as other similar organisms are
grouped together using a key.
 We can see how organisms are related in and evolutionary
way. By looking at organisms, which have similar anatomical
features, it is possible to see relationships on their
phylogenetic tree. DNA evidence confirms the anatomical
evidence for placing organisms in the same group.
 It allows for the prediction of characteristics shared by
members of a group.
 Biochemical Evidence for Common Anscestry
 Every known living organism on Earth uses DNA as its
main source of genetic information
 All the proteins found in living organisms use the same
20 amino acids to forms their polypeptide chains
 All the living organisms on Earth have left-handed
amino acids and none are right-handed, leading to the
belief that there is a common ancestor.
 If we compare the amino acid sequences of haemoglobin in
humans, cats and earthworms, we see that cats and humans have
greater similarities that humans and earthworms.
 This shows several trends:
 The more similar the biochemical evidence, the more interrelated
the species are
 The more similar the evidence, there is less time since the two
species had a common ancestor (ie. The ancestor of earthworms
lived a longer time ago than the ancestor of cats and human.)
 Changes in the DNA sequences of genes from one generation to
another are partly due to mutations and the more differences there
are between two species, the les closely related they are.
AAAATTTTCCCCGGGG
2. AAAATTTACCCCGGGG
3. AAAATTTACCCGCGGG
4. AACATCTTCCACGCTG
1.
1 and 2 have the
fewest differences in
their DNA and are
more closely related
 Cladogram
 Cladistics
 Clades
 Need to classify, taking into account:
 Homologous Characteristics
 Analogous Characteristics
Birds
Reptiles
 Fused clavicle
 Shoulder girdle
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(wishbone)
Flexible wrists
Hollow bones
Characteristic egg shell
Hip and leg structure,
notably with backward
pointed knees
 Strong skeletal system
 Lay eggs
 Lateral leg and hip
structure