Classification and Evolution

Question 1

What is classification?

Answer 1

Classification is the act of arranging organisms into groups based on their similarities and differences.
This makes it easier for scientists to identify them and to study them. Taxonomy is the study of classification. There are a few different classification systems in use, but they all involve placing organisms into groups in a taxonomic hierarchy:
1) There are eight levels of groups (called taxonomic groups) used in classification.
2) Similar organisms are first sorted into one of three very large groups called domains, e.g. animals, plants and fungi are in the Eukarya domain. 3) Similar organisms are then sorted into slightly smaller groups called kingdoms, e.g. all animals are in the animal kingdom. 4) Similar organisms from that kingdom are then grouped into a phylum. Similar organisms from each phylum are then grouped into a , and down the eight levels of the taxonomic hierarchy.
5) As you move down the hierarchy, there are more groups at each level but fewer organisms in each group.
6) The hierarchy ends with species — the groups that contain only one type of organism (e.g. humans, dog, E. coli and about 50 million other living species).

Question 2

What are the 8 levels of the taxonomic hierarchy?

Answer 2

Domain
Kingdom 
Phylum
Class
Order
Family 
Genus 
Species

Question 3

How many kingdoms are there?

Answer 3

5

Question 4

What are the 5 kingdoms?

Answer 4

Prokaryotae
Protoctista
Fungi
Plantae
Animalia

Question 5

What is an example of Prokaryotae and its features?

Answer 5

prokaryotic, unicellular (single-celled),
no nucleus, less than 5 µm

bacteria

Question 6

What is an example of Protoctista and its features?

Answer 6

eukaryotic cells, usually live in water, single-celled
or simple multicellular organisms

algae, protozoa

Question 7

What is an example of Fungi and its features?

Answer 7

eukaryotic, chitin cell wall, saprotrophic (absorb
substances from dead or decaying organisms),
single-celled or multicellular organisms

moulds, yeasts,
mushrooms

Question 8

What is an example of Plantae and its features?

Answer 8

can photosynthesise, contain chlorophyll,
autotrophic (produce their own food)

mosses, ferns,
flowering plants

Question 9

What is an example of Animalia and its features?

Answer 9

nematodes (roundworms),
molluscs, insects, fish,
reptiles, birds, mammals

eukaryotic, multicellular, no cell walls,
heterotrophic (consume plants and animals)

Question 10

Why Is The Binomial Naming System is Used in Classification

Answer 10

1) The nomenclature (naming system) used for classification is called the binomial system
— all organisms are given one internationally accepted scientific name in Latin that has two parts.
2) The first part of the name is the genus name and has a capital letter. The second part is the species
name and begins with a lower case letter. E.g. using the binomial system humans are Homo sapiens.
Names are always written in italics (or they’re underlined if they’re handwritten).
3) The binomial system helps to avoid the confusion of using common names. E.g. over 100 different
plant species are called raspberries and one species of buttercup has over 90 different common names.

Question 11

What is Phylogeny?

Answer 11

1) Phylogeny is the study of the evolutionary history of groups of organisms. Phylogeny tells us who’s related to whom and how closely related they are. 2) All organisms have evolved from
shared common ancestors (relatives). This can be shown on a
phylogenetic tree, 3) This tree shows the relationship
point between members of the Hominidae family (great apes and humans). The first branch point represents a common ancestor of all the family members. This ancestor is now extinct. Orangutans were the first group to diverge (evolve to become a different species) from this common ancestor. 4) Each of the following branch points represents another common ancestor from which a different
group diverged. Gorillas diverged next, then humans, closely followed by bonobos and chimpanzees. 5) According to phylogenetics, a species is the smallest group that shares a common ancestor — in other words, the end of a branch on a phylogenetic tree. 6) Closely related species diverged away from each other most recently. E.g. humans and chimpanzees are closely related, as they diverged very recently. You can see this because their branches are close together. Humans and orangutans are more distantly related, as they diverged longer ago, so their branches are further apart.

Question 12

Classification Systems are now Based on a?

Answer 12

Classification Systems are now Based on a Range of Evidence

Question 13

Why Observable Features aren’t Always Enough?

Answer 13

1) Early classification systems only used
observable features (things you can see)
to place organisms into groups,
e.g. whether they lay eggs, can fly
or can cook a mean chilli...
2) But this method has problems. Scientists
don’t always agree on the relative
importance of different features and
groups based solely on physical features
may not show how related organisms are.

Question 14

How does Other Evidence Shows How Similar Organisms are

Answer 14

Other Evidence Shows How Similar Organisms are
1) Classification systems are now based on observable features along with other evidence.
2) The more similar organisms are, the more related they are. We now use a wide range of evidence
to see , and therefore how related, organisms are.

Question 15

Why Does New Technology Means New Discoveries

Answer 15

New Technology Means New Discoveries
1) New technologies (e.g. new DNA techniques,
better microscopes) can result in new
discoveries being made and the relationships
between organisms being clarified.
2) Scientists can share their new discoveries in
meetings and scientific journals (see p. 2).
How organisms are classified is continually
revised to take account of any new findings
that scientists discover.

Question 16

What is Five Kingdoms Vs Three Domains?

Answer 16

Five Kingdoms Vs Three Domains

The five kingdom classification system has now been replaced with the three domain system

Question 17

What is the 3 domain system?

Answer 17

1) In the older system the largest groups were the five kingdoms — all
organisms were placed into one of these groups. 2) In 1990, the three domain system was proposed. This new system has three domains — large super kingdoms that are above the kingdoms in the taxonomic hierarchy. 3) In the three domain system, organisms that were in
the kingdom Prokaryotae (which contains unicellular organisms without a nucleus) are separated into two domains — the Archaea and Bacteria. 4) Organisms with cells that contain a nucleus are placed in the domain Eukarya (this includes four of the five kingdoms). 5) The lower hierarchy stays the same — Kingdom, Phylum, Class, Order, Family, Genus, Species.

Question 18

How Did Molecular Evidence Led to the Proposal of the Three Domain System

Answer 18

Molecular Evidence Led to the Proposal of the Three Domain System
1) The three domain system was proposed because of new evidence, mainly molecular. E.g. the Prokaryotae were reclassified into two domains because new evidence showed large differences between the Archaea and Bacteria. The new evidence included: Molecular evidence — The enzyme RNA polymerase (needed to make RNA) is different in Bacteria and Archaea. Archaea, but not Bacteria, have similar histones (proteins that bind to DNA) to Eukarya.
• Cell membrane evidence — The bonds of the lipids in the cell membranes of Bacteria and Archaea are different. The development and composition of flagellae are also different. 2) Most scientists now agree that Archaea and Bacteria evolved separately and that Archaea are more closely related to Eukarya than Bacteria. The three domain system reflects how different the Archaea and Bacteria are.
3) The development of the three domain system is an example of how scientific knowledge is always changing and improving

Question 19

What is variation?

Answer 19

Variation is the differences that exist between individuals. Every individual organism is unique — even clones (such as identical twins) show some variation.

Question 20

What 2 ways can variation occur?

Answer 20

Within a species

between a species

Question 21

What is variation within a species?

Answer 21

1) Within species —Variation within a species is called intraspecific variation. For example,individual European robins weigh between 16 g and 22 g and show some variation in many other characteristics including length, wingspan, colour and beak size.

Question 22

Whats variation between species?

Answer 22

2) Between species — The variation between different species is called interspecific variation. For example, the lightest species of bird is the bee hummingbird, which weighs around 1.6 g on average. The heaviest species of bird is the ostrich, which can weigh up to 160 kg (100 000 times as much).

Question 23

What is continuous variation?

Answer 23

Continuous variation is when the individuals in a population vary within a range — there are no distinct categories, e.g. humans can be any height within a range (139 cm, 175 cm, 185.9 cm, etc.), not just tall or short.
Here are some more examples: are not distinct
Animals
1) Milk yield — e.g. cows can produce any volume of milk within a range. 2) Mass — e.g. humans can be any mass within a range.

Plants
1) Number of leaves — e.g. a tree can have any number of leaves within a range. 2) Mass — e.g. the mass of the seeds from a flower head varies within a range.

Microorganisms

1) Width — e.g. the width of E. coli bacteria varies within a range.
2) Length — e.g. the length of the flagellum can vary within a range.

Question 24

Whats discontinuous variation?

Answer 24

Discontinuous variation is when there are two or more distinct
categories — each individual falls into only one of these
categories, there are no intermediates. Here are some examples:

Animals Blood group
Plants
1) Colour — e.g. courgettes are either yellow, dark green or light green. 2) Seed shape — e.g. some pea plants have smooth seeds and some have wrinkled seeds.
Microorganisms
1) Antibiotic resistance — e.g. bacteria are either resistant or not.
2) Pigment production — e.g. some types of bacteria can produce a coloured pigment, some can’t.

Question 25

What 2 factors can cause variation

Answer 25

genetic, environmental both?

Question 26

How can genetic factors cause variation?

Answer 26

1
Genetic factors
1) Different species have different genes.
2) Individuals of the same species have the same genes,
but different versions of them (called alleles).
3) The genes and alleles an organism has make up its genotype.
4) The differences in genotype result in variation in phenotype
— the characteristics displayed by an organism.
5) Examples of variation caused only by genetic factors
include blood group in humans (O, A, B or AB) and
antibiotic resistance in bacteria.
6) You inherit your genes from your parents. This means
variation caused by genetic factors is inherited.

Question 27

How can environmental factors cause variation?

Answer 27

1) Variation can also be caused by differences in the environment,
e.g. climate, food, lifestyle. 2) Characteristics controlled by
environmental factors can change over an organism’s life. 3) Examples of variation caused only by environmental factors include accents and whether people have pierced ears.

Question 28

How can both environmental and genetic factors cause variation?

Answer 28

Both Genetic factors determine the characteristics an organism’s born with, but environmental factors can influence how some characteristics develop. For example:
1) Height — genes determine how tall an organism can grow (e.g. tall parents tend to have tall children). But diet or nutrient availability affect how tall an organism actually grows. 2) Flagellum — genes determine if a microorganism can grow a flagellum, but some will
only start to grow them in certain environments, e.g. if metal ions are present.

Question 29

How can You Can Use the Mean to Look for Variation Between Samples?

Answer 29

1) To investigate variation you usually take samples of a population 2) The mean is an average of the values collected in a sample. It can
be used to tell if there is variation between samples. For example:
The mean height of a species of tree in woodland A = 26 m, in woodland B = 32 m and in woodland C = 35 m. So the mean height varies. 3) Most samples will include values either side of the mean, so you end up with a bell-shaped graph — this is called a normal distribution. A normal distribution is symmetrical about the mean.

Question 30

What does The Standard Deviation Tells You About Variation Within a Sample?

Answer 30

1) The standard deviation tells you how much the values in a single sample vary. It’s a measure of the spread of values about the mean.
mean 2) Sometimes you’ll see the mean written as, e.g. 9 ± 3.
This means that the mean is 9 and the standard deviation
is 3, so most of the values are spread between 6 and 12.
mean 3) A large standard deviation means the values in the sample vary a lot. A small standard deviation tells you that most of the sample data is around the mean value, so varies little.

Question 31

Standard deviation equation?

Answer 31

s=√Σ(x-x̄)^2/ n-1

Σ sum of
‘x’ stands for a value in the mean data set, and ‘x’ is the .
x̄) ‘ means the mean

Question 32

What does being adapted to an environment mean?

Answer 32

Adaptations make Organisms Well Suited to Their Environment
1) Being adapted to an environment means an organism has features that increase its chances of survival and reproduction, and also the chances of its offspring reproducing successfully. 2) These features are called adaptations and can be behavioural, physiological and anatomical. 3) Adaptations develop because of evolution by natural selection 4) In each generation, the best-adapted individuals are more likely to survive and reproduce — passing their adaptations on to their offspring. Individuals that are less well adapted are more likely to die before reproducing.

Question 33

What 3 things can adaptions be?

Answer 33

Behavioral
Physiological
Anatomical

Question 34

What are Behavioral adaption?

Answer 34

Behavioural adaptations
Ways an organism acts that increase its chance of survival. For example: • Possums sometimes ‘play dead’ — if they’re being threatened by a predator they play dead to escape attack. This increases their chance of survival. • Scorpions dance before mating — this makes sure they attract a mate of the same species, increasing the likelihood of successful mating.

Question 35

What are Physiological adaptations

Answer 35

Physiological adaptations
Processes inside an organism’s body that increase its chance of survival. For example: • Brown bears hibernate — they lower their rate of metabolism (all the chemical reactions taking place in their body) over winter. This conserves energy, so they don’t need to
look for food in the months when it’s scarce — increasing their chance of survival. • Some bacteria produce antibiotics — these kill other species of bacteria in the area. This means there’s less competition, so they’re more likely to survive.

Question 36

What are Anatomical (structural) adaptations?

Answer 36

Anatomical (structural) adaptations
Structural features of an organism’s body that increase its chance of survival. For example: • Otters have a streamlined shape — making it easier to glide through the water. This makes it easier for them to catch prey and escape predators, increasing their chance of survival.
• Whales have a thick layer of blubber (fat) — this helps to keep them warm in the cold sea. This increases their chance of survival in places where their food is found.

Question 37

Why do different taxonomic groups have similar features?

Answer 37

Different Taxonomic Groups May Have Similar Features

1) Organisms from different taxonomic groups may have similar features even though they’re not closely related — for example, whales and sharks 2) This is usually because the organisms have evolved in similar environments and to fill similar ecological niches.
3) The example you need to learn for your exam is of marsupial and placental moles

Question 38

How many types of mammals are there?

Answer 38

3

Question 39

What are the three types of mammals?

Answer 39

1) There are three different groups of mammals. Most mammals are placental mammals,
while some are marsupials (and a very few are egg-laying monotremes).
2) Marsupials are found mainly in Australia and the Americas. They diverged from placental mammals
many millions of years ago and have been evolving separately ever since.

Question 40

What are marsupials?

Answer 40

Marsupial mammals (e.g. kangaroos):
• have a short gestation period (pregnancy).
• don’t develop a full placenta.
• are born early in their development and
climb into their mother’s pouch. Here they
become attached to a teat and receive milk
while they continue to develop.

Question 41

What are Placental mammals?

Answer 41

Placental mammals (e.g. humans):
• have a longer gestation period.
• develop a placenta during pregnancy,
which allows the exchange of
nutrients and waste products
between the fetus and the mother.
• are born more fully developed.

Question 42

Why are Marsupial and Placental Moles Look Alike But Aren’t Closely Related?

Answer 42

Marsupial and Placental Moles Look Alike But Aren’t Closely Related
1) Marsupial moles and placental moles aren’t closely related —
they evolved independently on different continents.
2) They do share similar anatomical features though (i.e. they look alike).
That’s because they’ve both evolved to live in similar environments:
Both types of mole live in tunnels in the ground. They burrow to reach their food supply
(e.g. earthworms, insects and other invertebrates). Their adaptations to this lifestyle include:
• Small or nonexistent eyes because they don’t need to be able to see underground.
• No external ears, to keep a streamlined head for burrowing.
• Scoop-shaped and powerful front paws, which are good for digging.
• Claws that are specialised for digging.
• A tube shaped body and cone shaped head, which makes it easier to push through sand or soil.

Question 43

Darwin Published his Theory of Evolution by Natural Selection in?

Answer 43

Darwin Published his Theory of Evolution by Natural Selection in 1859

Question 44

What was Darwin’s 4 key observations about the world around him?

Answer 44

Observations:

1) Organisms produce more offspring than survive.
2) There’s variation in the characteristics of members of the same species.
3) Some of these characteristics can be passed on from one generation to the next.
4) Individuals that are best adapted to their environment are more likely to survive.

Question 45

What was Darwin’s theory?

Answer 45

Theory: 1) Individuals within a population show variation in their phenotypes (their characteristics). 2) Selection pressures (environmental factors such as predation, disease and competition) create a struggle for survival. 3) Individuals with better adaptations (characteristics that give a selective advantage, e.g. being able to run away from predators faster) are more likely to survive and have reproductive success — in other words, they reproduce and pass on their advantageous adaptations to their offspring. 4) Over time, the proportion of the population possessing the advantageous adaptations increases. 5) Over generations this leads to evolution as the favourable adaptations become more common in the population.

1) We now know that genes determine many of an organism’s characteristics and that individuals show
variations in their phenotypes partly as a result of genetic variation, i.e. the different alleles they have.
2) When an organism with advantageous characteristics reproduces, the alleles that determine those characteristics may be passed on to its offspring.

Question 46

How did Wallace Contribute to the Theory of Evolution?

Answer 46

Wallace Contributed to the Theory of Evolution
Alfred Russel Wallace, a scientist working at the same time as Darwin, played
an important part in developing the theory of evolution by natural selection.
• He independently came up with the idea of natural selection and wrote to Darwin about it.
• He and Darwin published their papers on evolution together and acknowledged each other’s
work — although they didn’t always agree about the mechanisms involved in natural selection.
• Wallace’s observations provided lots of evidence to support the theory of evolution by
natural selection. For example, he realised that warning colours are used by some species
(e.g. butterflies) to deter predators from eating them and that this was an example of an
advantageous adaptation that had evolved by natural selection.

Question 47

What 3 ways support evolution?

Answer 47

Fossil record evidence
DNA evidence
molecular evidence

Question 48

What is Fossil Record Evidence

Answer 48

Fossil Record Evidence
Example — The fossil record of the
horse shows a gradual change in
characteristics, including increasing
size and hoof development.

Fossils are the remains of organisms preserved in rocks.
By arranging fossils in chronological (date) order, gradual changes
in organisms can be observed that provide evidence of evolution.

Question 49

What is DNA evidence?

Answer 49

1) The theory of evolution suggests that all organisms have evolved from shared common ancestors.
2) Closely related species diverged (evolved to become different species) more recently.
3) Evolution is caused by gradual changes in the base sequence of an organisms’ DNA.
4) Organisms that diverged away from each other more recently, should have more similar DNA, as less time has passed for changes in the DNA sequence to occur. This is exactly what scientists have found.
Example — Humans, chimps and mice all evolved from a common ancestor. Humans and mice diverged a long time ago, but humans and chimps diverged quite recently. The DNA base sequence of humans and chimps is 94% the same, but human and mouse DNA is only 85% the same. Common ancestor In eukaryotes, most DNA is found in the cell nucleus. But scientists don’t just analyse nuclear DNA to find out about evolutionary relationships. Eukaryotic organisms also have DNA in their mitochondria, so scientists can also look at differences in mitochondrial DNA to see how closely related organisms are.

Question 50

What is molecular evidence?

Answer 50

Molecular Evidence
In addition to DNA, the similarities in other molecules provide evidence.
Scientists compare the sequence of amino acids in proteins, and compare antibodies.
Organisms that diverged away from each other more recently have more similar molecules,
as less time has passed for changes in proteins and other molecules to occur.

Question 51

Why can Populations of Insects can Evolve Resistance to Pesticides?

Answer 51

Pesticides are chemicals that kill pests (e.g. insects that damage crops). Scientists have observed the evolution of pesticide resistance in many species of insect. For example, some populations of mosquito have evolved resistance to the pesticide DDT. Some populations of pollen beetles (which damage the crop oilseed rape) are resistant to pyrethroid pesticides.
The evolution of pesticide resistance can be explained by natural selection:
1) There is variation in a population of insects. Genetic mutations create alleles that make some insects naturally resistant to a pesticide.
2) If the population of insects is exposed to that pesticide only
the individuals with resistance will survive to reproduce.
3) The alleles which cause the pesticide resistance will be passed on
to the next generation, and so the population will evolve — more
individuals will carry the allele than in the previous generation.

Question 52

Why Is The Evolution of Pesticide Resistance has Implications for Humans

Answer 52

The Evolution of Pesticide Resistance has Implications for Humans

1) Crop infestations with pesticide-resistant insects are harder to control — some insects are resistant to lots of different pesticides. It takes farmers a while to figure out which pesticide will kill the insect and in that time all the crop could be destroyed. If the insects are resistant to specific pesticides (ones that only kill that insect), farmers might have to use broader pesticides (those that kill a range of insects), which could kill beneficial insects.
2) If disease-carrying insects (e.g. mosquitoes) become pesticide-resistant, the spread of disease could increase.
3) A population of insects could evolve resistance to all pesticides in use. To prevent this new pesticides need to be produced. This takes time and costs money.