Topic 5 Evolution

Question 1

Define “evolution”

5.1

Answer 1

Evolution occurs when heritable characteristics of a species change.

the cumulative change in the heritable characteristics of a population over time

Cumulative change: small changes over many generation

Understandings: Evolution occurs when heritable characteristics of a species change.

Question 2

Define “heritable characteristics”

5.1

Answer 2

gene-controlled factors that are passed down from parents to offspring

Understanding: Evolution occurs when heritable characteristics of species change.

Question 3

Define “fossil record”

5.1

Answer 3

A fossil record is a group of fossils which has been analyzed and arranged in chronological and/or taxonomic order.

Understanding: The fossil record provides evidence for evolution.

Question 4

Define “strata” in relation to the fossil record

5.1

Answer 4

Fossils are often contained in rocks that build up in layers called strata. The strata provide relative timeline, with layers near the top being newer and layers near the bottom being older.

Understanding: The fossil record provides evidence for evolution.

Question 5

Outline how fossils provide that evolution has occurred

5.1

Answer 5

The sequence in which organisms appear in the fossil record
matches their complexity: with bacteria and
simple algae appearing first, fungi and worms
later and land vertebrates later.

The sequence also fts in with the ecology of the groups: plant fossils appearing before animal, plants on land before animals on land, and plants suitable for insect pollination beore insect pollinators.

Understanding: The fossil record provides evidence for evolution.

Question 6

Define “selective breeding”

5.1

Answer 6

Selective breeding (also called artificial selection) is the process by which humans breed animals and plants for particular traits

Understanding: Selective breeding of domesticated animals shows that artificial selection can cause evolution.​

Question 7

Explain the process of selective breeding

5.1

Answer 7

1. Individuals which show the most desirable traits are chosen to breed together.
2. The next generation will have an increased frequency of the desired trait.
3. The process is repeated for many generations until the entire population shows the desired trait

Understanding: Explain the process of artificial selection using selective breeding.

Question 8

Outline how artificial selection can serve as evidence for evolution.

5.1

Answer 8

Selective breeding provides evidence of evolution as targeted breeds can show significant variation in a (relatively) short period.

Understanding: Explain the process of artificial selection using selective breeding.

Question 9

Use an example to explain how selective breeding has lead to evolution in an animal species.

5.1

Answer 9

• Farmers breed animals in order to improve productivity (and thus profits).
• For example, dairy farmers will look for the cows that can produce the most milk and only breed those cows.
• These cows then pass their genes that contribute to higher milk production onto their offspring, increasing milk productivity each generation.

Understanding: Selective breeding of domesticated animals shows that artificial selection can cause evolution.​

Question 10

Define “homologous structure.”

5.1

Answer 10

Homologous structures are similar in structure but different in function. Homologous structures imply a common ancestor.

Understanding: Evolution of homologous structures by adaptive radiation explains similarities in structure when there are differences in function.​

Question 11

Define “adaptive radiation.”

5.1

Answer 11

Similar organisms adapting to different environments/needs.

Understanding: Evolution of homologous structures by adaptive radiation explains similarities in structure when there are differences in function.​

Question 12

Define “convergent evolution”.

5.1

Answer 12

Different organisms adapting to similar environments.

Understanding: Evolution of homologous structures by adaptive radiation explains similarities in structure when there are differences in function.​

Question 13

Define “analogous structures “.

5.1

Answer 13

Analogous structures are similar in function but differ in structure.
* Analogous structures do not show common ancestry

Understanding: Evolution of homologous structures by adaptive radiation explains similarities in structure when there are differences in function.​

Question 14

Contrast analogous structures and homologous structures.

5.1

Answer 14

Homologous structures: structures that are similar in organisms because they were inherited from a common ancestor.

Analogous structures: structures that are similar but were not inherited from a common ancestor, the organisms independently evolved the characteristic (via convergent evolution).Different organisms adapting to similar environments.

Understanding: Evolution of homologous structures by adaptive radiation explains similarities in structure when there are differences in function.​

Question 15

Define “vestigial structure.”

5.1

Answer 15

Reduced structures that serve no function.
* These structures are explained by evolution as structures that no longer have a function and so are being gradually lost.

Understanding: Evolution of homologous structures by adaptive radiation explains similarities in structure when there are differences in function.​

Question 16

Define “speciation.”

5.1

Answer 16

Speciation is the process by which populations evolve to become distinct species that are reproductively isolated (no longer capable of interbreeding with each other to produce fertile offspring).

Understanding: Populations of a species can gradually diverge into separate species by evolution.​

Question 17

Describe the process of speciation.

5.1

Answer 17

1. Two populations of a species become separated (eg. geographically) so that they do not interbreed.
2. Natural selection then acts differently on the two populations, they will evolve in different ways.
3. The characteristics of the two populations will gradually diverge. After a time they will be recognizably different.
4. If the populations subsequently merge and have the chance of interbreeding, but do not actually interbreed, it would be clear that they have evolved into separate species.

Understanding: Populations of a species can gradually diverge into separate species by evolution.​

Question 18

Explain how continuous variation across the geographical range of related populations matches the concept of gradual divergence.

5.1

Answer 18

Because species can gradually diverge over long periods of time and there is no sudden switch from being two populations of one species to being two separate species, the decision to lump populations together or split them into separate species remains rather arbitrary.

The continuous range in variation between populations does not match either the belief that species were created as distinct types of organism and therefore should be constant across their geographic range or that species are unchanging. Instead it provides evidence for the evolution of species and the origin of new species by evolution.

Understanding: Continuous variation across the geographical range of related populations matches the concept of gradual divergence.

Question 19

Explain how continuous variation across geographical ranges is evidence of evolutionary change.

5.1

Answer 19

Natural selection causes adaptation to the local environment, resulting in different genotypes or phenotypes being favoured in different environments.

Through natural selection acting on populations in localized regions, genetic differences between populations may accumulate. The populations will gradually diverge. If the differences between populations become great enough, it may lead to speciation.

Understanding: Continuous variation across the geographical range of related populations matches the concept of gradual divergence.

Question 20

Explain how natural selection leads to changes in the melanistic variety of insects in polluted areas.

5.1

Answer 20

• In unpolluted areas tree branches are covered in pale-coloured lichens and peppered moths are well camoufaged against predators.
• Sulphur dioxide pollution kills lichens and soot from coal burning blackens tree branches.
• Therefore, melanic moths are well camoufaged against dark tree branches in polluted areas.
• In polluted areas the melanic variety of Biston betularia replaced the peppered variety over a relatively short time, but not in non- polluted areas.

Application: Development of melanistic insects in polluted areas.

Question 21

Relate differences in pentadactyl limb structures to differences in limb function.

5.1

Answer 21

The pentadactyl limb in vertebrates is an example of a homologous structure.
* Human arms are adapted for tool manipulation and grasping
* Bird and bat wings are adapted for flying
* Horse hooves are adapted for galloping
* Whale and dolphin fins are adapted for swimming

This pattern is an indication of a common ancestor.

Application: Comparison of the pentadactyl limb of mammals, birds,
amphibians and reptiles with different methods of locomotion.

Question 22

Define “variation.”

5.2

Answer 22

Variation is the genetic differences among individuals.
* Species that only carry out asexual reproduction can only rely on mutation for variation

Understanding: Natural selection can only occur if there is variation among members of the same species.

Question 23

Define “natural selection.”

5.2

Answer 23

Natural selection is a process of evolution in which organisms better adapted to their environment tend to survive and produce more offspring.

Understanding: Natural selection can only occur if there is variation among members of the same species.

Question 24

Outline the conditions required for natural selection.

5.2

Answer 24

• Variation in characteristics of individuals
• Heredity of characteristics
• Reproduction of more offspring than the environment can support (compitition)
• Variation in fitness (ability of an organism to survive and reproduce)

Understanding: Natural selection can only occur if there is variation among members of the same species.

Question 25

Outline the process of natural selection.

5.2

Answer 25

1. Species tend to produce more ospring than the
   environmentcan support.
2. There is a struggle for existence in which some individuals
   survive and some die.
3. In natural populations there is variation between the
   individuals.
4. Some individuals are betteradapted than others. An
   adaptation is a characteristic that makes an individual
   suited to its environment and way of life.
5. Individuals thatare betteradapted tend to survive
   and produce more offspring, while less well adapted
   individuals tend to die or produce fewer ofspring so each
   generation contains more ofspring of better adapted than
   less well adapted individuals.
6. Individuals that reproduce pass on characteristics to their
   ofspring.
7. The frequency of characteristics that make individuals
   betteradapted increases and the frequencies of other
   characteristics decrease, so species change and become
   betteradapted.

Understanding: Natural selection can only occur if there is variation among members of the same species.

Question 26

Explain why natural selection can only function if there is variation in a species.

5.2

Answer 26

Natural selection acts on the genetic variation between individuals in a population. Some individuals will have advantageous variations that are better adapted to the environmental conditions. Individuals with the beneficial variation will have a greater chance of survival and reproduction than others. The favorable genetic variation will be inherited by offspring in the next generation.

Understanding: Natural selection can only occur if there is variation among members of the same species.

Question 27

List sources of genetic variation.

5.2

Answer 27

• Random mutation
• Sexual reproduction (meiosis and random fertilisation)

Understanding: Mutation, meiosis and sexual reproduction cause variation between individuals in a species.

Question 28

Outline how mutation leads to genetic variation.

5.2

Answer 28

Mutation is the original source of variation. New alleles are produced by gene mutation, which enlarges the gene pool of a population.

Understanding: Mutation, meiosis and sexual reproduction cause variation between individuals in a species.

Question 29

Outline how meiosis leads to genetic variation.

5.2

Answer 29

Meiosis produces new combinations of alleles by breaking up the existing combination in a diploid cell. Every cell produced by meiosis in an individual is likely to carry a different combination of alleles, because of crossing over and the independent orientation of bivalents.

Understanding: Mutation, meiosis and sexual reproduction cause variation between individuals in a species.

Question 30

Outline how sexual reproduction leads to genetic variation.

5.2

Answer 30

Sexual reproduction involves the fusion of male and female gametes. The gametes usually come from different parents, so the offspring has a combination of alleles from two individuals. This allows mutations that occurred in different individuals to be brought together.

Understanding: Mutation, meiosis and sexual reproduction cause variation between individuals in a species.

Question 31

Define “adaptation.”

5.2

Answer 31

Adaptations are structures/characteristics that make an individual suited to its environment or way of life.

Understanding: Adaptations are characteristics that make an individual suited to its environment and way of life.

Question 32

Explain the consequences of populations producing more offspring than the environment can support.

5.2

Answer 32

Populations producing more offspring than the environment can support will tend to **lead to a struggle for existence within a population. There will be competition for resources and not every individual will obtain enough to allow them to survive and reproduce.

Understanding: Species tend to produce more offspring than the environment can support.​

Question 33

Explain the effect of the selective pressure on the more and less adapted individuals in a population.

5.2

Answer 33

In the struggle for existence the less well-adapted individuals tend to die or fail to reproduce and the best adapted tend to survive and produce many offspring.
* The frequency of the more adapted trait will increase in the population while frequency of the less adapted trait will decrease in the population.

Understanding: Individuals that are better adapted tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring

Question 34

Contrast acquired characteristics with inheritable characteristics.

5.2

Answer 34

**Inherited characteristics **: genetically passed down from parents to their offspring.

Acquired characteristic: gained by an organism after birth due to environmental influence.

Understanding: Individuals that reproduce pass on characteristics to their offspring.​

Question 35

Outline why only inherited characteristics can be acted upon by natural selection.

5.2

Answer 35

Acquired traits are not within the genetic material of an individual and therefore they cannot be passed down to offspring during reproduction. In order to be acted upon natural selection, the trait must be able to be inherited by the subsequent generation.

Understanding: Individuals that reproduce pass on characteristics to their offspring.​

Question 36

Compare the reproductive success of better and less well adapted individuals in a population.

5.2

Answer 36

Individuals more adapted to the selective pressure will will be able to survive and reproduce, passing on the trait to the subsequent generation. The frequency of the more adapted trait will increase in the population.

Individuals less adapted to the selective pressure will not survive and/or reproduce. The frequency of the less adapted trait will decrease in the population.

Understanding: Natural selection increases the frequency of characteristics that make individuals better adapted and decreases the frequency of other characteristics leading to changes within the species.

Question 37

Outline the role of Charles Darwin in the study of Galapagos finches.

5.2

Answer 37

• He observed that the beaks of finches varied and so did their diet.
• Darwin hypothesized that the finches had originated from one species which had evolved into many different species on the different islands.

Application: Changes in beaks of finches on Daphne Major.

Question 38

Explain how natural selection leads to changes in the beaks of Galapagos finches with changes in weather conditions.

5.2

Answer 38

In 1977, an extended drought changed the frequency of larger beak sizes within the population by natural selection
* Dry conditions result in plants producing larger seeds with tougher seed casings
* Between 1976 and 1978 there was a change in average beak depth within the finch population
* Finches with larger beaks were better equipped to feed on the seeds and thus produced more offspring with larger beaks

Application: Changes in beaks of finches on Daphne Major.

Question 39

Explain how natural selection leads to changes in antibiotic resistance.

5.2

Answer 39

• When treated with antibiotics, the resistant bacteria will survive and reproduce by binary fission (asexual reproduction)
• The antibiotic resistant bacteria will flourish in the absence of competition from other strains of bacteria (killed by antibiotic)
• Antibiotic resistant bacteria may also confer resistance to susceptible strains by transferring plasmids via bacterial conjugation
• The introduction of antibiotic (selection pressure) has caused the antibiotic resistance gene to become more frequent (evolution)

Application: Evolution of antibiotic resistance in bacteria.

Question 40

List reasons why evolution of antibiotic resistance has been rapid.

5.2

Answer 40

• Evolution of antibiotic resistance has been rapid because bacteria reproduce very rapidly and have high mutation rate.
• Additionally, there has been extensive use of antibiotics since they were first discovered

Application: Evolution of antibiotic resistance in bacteria.

Question 41

Define “binomial nomenclature.”

5.3

Answer 41

Species are named with two name (binomial). The first name is for the genus and the second name is for the species. Together the two names make a unique combination that designate a species.

Understanding: The binomial system of names for species is universal among biologists and has been agreed and developed at a series of congresses.

Question 42

Outline the benefits of using a system of binomial nomenclature.

5.3

Answer 42

• It allows for the identification and comparison of organisms based on recognised characteristics
• It allows all organisms to be named according to a globally recognised scheme
• It can show how closely related organisms are, allowing for the prediction of evolutionary links
• It makes it easier to collect, sort and group information about organisms

Understanding: The binomial system of names for species is universal among biologists and has been agreed and developed at a series of congresses.

Question 43

State rules of binomial nomenclature formatting.

5.3

Answer 43

According to the binomial system of nomenclature, every organism is designated a scientific name with two parts:
* Genus is written first and is capitalised (e.g. Homo)
* Species follows and is written in lower case (e.g. Homo sapiens)
* Some species may occasionally have a sub-species designation (e.g. Homo sapiens sapiens – modern man)

Understanding: When species are discovered they are given scientific names using the binomial system

Question 44

Outline the benefit of a binomial system to identify a species.

5.3

Answer 44

The scientific naming system allows scientists to communicate about species without confusion that stems from using the names that arise from local language and culture.

NOS: Cooperation and collaboration between groups of scientists - scientists use the binomial system to identify a species rather than the many different local names.​

Question 45

Define “taxa”.

5.3

Answer 45

Taxon, plural taxa, is a grouping unit used in biological classification. There are multiple common grouping units of taxa. For example, a “species” is a taxon (group) of all the organisms that can (actually or potentially) interbreed with each other to produce fertile offspring and cannot breed with others.

Understanding: Taxonomists classify species using a hierarchy of taxa.​

Question 46

Outline the three domains of life.

5.3

Answer 46

• Eukarya – eukaryotic organisms that contain a membrane-bound nucleus (includes protist, plants, fungi and animals)
• Archaea – prokaryotic cells lacking a nucleus and consist of the extremophiles (e.g. methanogens, thermophiles, etc.)
• Eubacteria – prokaryotic cells lacking a nucleus and consist of the common pathogenic forms (e.g. E. coli, S. aureus, etc.)

Understanding: All organisms are classified into three domains.

Question 47

State the two prokaryotic domains.

5.3

Answer 47

Two domains consist of prokaryotic organisms, single-celled microorganisms whose cells have no nucleus or internal membrane bound compartments.
1. Archaea
2. Eubacteria

Understanding: All organisms are classified into three domains.

Question 48

Distinguish the archaea domain from the eubacteria domain.

5.3

Answer 48

Archaea:
* Proteins similar to histones bound to DNA
* Introns present in some genes
* Cell wall not made of peptidoglycan

Bacteria:
* Histones associated with DNA are absent
* Introns are rare or absent
* Cell wall made of chemical called peptidoglycan

Understanding: All organisms are classified into three domains.

Question 49

List the hierarchy of biological taxa, from largest to smallest.

5.3

Answer 49

The hierarchy of taxa from largest to smallest is:
1. Domain
2. Kingdom
3. Phylum
4. Class
5. Order
6. Family
7. Genus
8. Species

Understanding: The principal taxa for classifying eukaryotes are kingdom, phylum, class, order, family and genus and species.

Question 50

Define “natural classification.”

5.3

Answer 50

Natural classification groups together species that share a common ancestor from which they evolved. This is called the Darwinian principle of common descent.

Understanding: In a natural classification, the genus and accompanying higher taxa consist of all the species that have evolved from one common ancestral species.

Question 51

Define “artificial classification”.

5.3

Answer 51

**Artificial classification is the grouping of organisms into groups on the basis of observable structural features **(e.g. the grouping together of plants according to the number and situation of their stamens, styles, and stigmas rather than their evolutionary relationships).

Understanding: In a natural classification, the genus and accompanying higher taxa consist of all the species that have evolved from one common ancestral species.

Question 52

List difficulties in determining the natural classification of species.

5.3

Answer 52

• It is not always clear which groups of species do share a common ancestor, so natural classifcation can be problematic.
• Convergent evolution can make distantly related organisms appear superfcially similar and adaptive radiation can make related organisms appear different.

Understanding: In a natural classification, the genus and accompanying higher taxa consist of all the species that have evolved from one common ancestral species.

Question 53

List two situations in which the reclassification of a species may be necessary.

5.3

Answer 53

1. Sometimes new evidence indicates that members of a taxa do not share a common ancestor and therefore should not be grouped together in a natural classification scheme.
2. Sometimes new evidence indicates that species that were not thought to be related actually do share a common ancestor and therefore should grouped together in a natural classification scheme.

Understanding: Taxonomists sometimes reclassify groups of species when new evidence shows that a previous taxon contains species that have evolved from different ancestral species.

Question 54

Explain an advantages of natural classification.

5.3

Answer 54

• Identifcation of species is easier. If a specimen of an organism is found and it is not obvious what species it is, the specimen can be identifed by assigning it first to its kingdom, then the phylum within the kingdom, class within the phylum and so on down to species level. Dichotomous keys can be used to help with this process.
• Because all of the members of a group in a natural classifcation have evolved from a common ancestral species, they inherit similar characteristics. This allows prediction of the characteristics of species within a group.

Understanding: Natural classification helps in identification of species and allows the prediction of characteristics shared by species within a group.

Question 55

State the classification of a plant, from domain to species.

5.3

Answer 55

Domain: Eukaryota (all eukaryotic celled organisms)
Kingdom: Plantae (all plants)
Phylum: Angiospermatophyta (all flowering plants)
Class: Dicotyledonae (plants two to seed cotyledons)
Order: Rosales (all roses and rose like plants)
Family: Rosaceae (all roses)
Genus: Rosa
Species: gallica

Application: Classification of one plant and one animal species from domain to species level.

Question 56

State the classification of an animal, from domain to species.

5.3

Answer 56

Domain: Eukaryota (all eukaryotic celled organisms)
Kingdom: Animalia (all animals)
Phylum: Chordata (all animals with a hollow nerve cord)
Class: Mammalia (all animals the nurse their young)
Order: Carnivora (animals with teeth for tearing meat)
Family: Felidae (cats with retractable claws)
Genus: Felis (non-roaring cats)
Species: domesticus (domesticated pet cats)

Application: Classification of one plant and one animal species from domain to species level.

Question 57

State the four major plant phyla.

5.3

Answer 57

• Bryophyta (mosses)
• Filicinophyta (ferns)
• Coniferophyta (conifers)
• Angiospermatophyta (flowering plants)

Application: Recognition features of bryophyte, filicinophyta, coniferophyta, and angiospermophyta.

Question 58

Outline the characteristics of the bryophyta.

5.3

Answer 58

Vegetative organs - parts of the plant concerned with growth rather than reproduction
* Rhizoids but no true roots. Some with simple stems and leaves; others have only a thallus

Vascular tissue
* No xylem or phloem

Cambium - cells between xylem and phloem that can produce more of these tissues
* No cambium; no true trees and shrubs

Pollen - small structures containing male gametes that are dispersed
* Pollen is not produced

Ovules - contains a female gamete and develops into a seed after fertilization
* No ovaries or ovules

Seeds - dispersible unit consisting of an embryo plant and food reserves
* No seeds

Fruits
* No fruits

Application: Recognition features of bryophyte, filicinophyta, coniferophyta, and angiospermophyta.

Question 59

Outline the characteristics of the filicinophyta.

5.3

Answer 59

Vegetative organs - parts of the plant concerned with growth rather than reproduction
* Roots, stems and leaves are usually present

Vascular tissue
* Xylem and phloem are both present

Cambium - cells between xylem and phloem that can produce more of these tissues
* No cambium; no true trees and shrubs

Pollen - small structures containing male gametes that are dispersed
* Pollen is not produced

Ovules - contains a female gamete and develops into a seed after fertilization
* No ovaries or ovules

Seeds - dispersible unit consisting of an embryo plant and food reserves
* No seeds

Fruits
* No fruits

Application: Recognition features of bryophyte, filicinophyta, coniferophyta, and angiospermophyta.

Question 60

Outline the characteristics of the coniferophyta.

5.3

Answer 60

Vegetative organs - parts of the plant concerned with growth rather than reproduction
* Roots, stems and leaves are usually present

Vascular tissue
* Xylem and phloem are both present

Cambium - cells between xylem and phloem that can produce more of these tissues
* Present

Pollen - small structures containing male gametes that are dispersed
* Pollen is produced in male cones

Ovules - contains a female gamete and develops into a seed after fertilization
* Ovules are produced in female cones

Seeds - dispersible unit consisting of an embryo plant and food reserves
* Seeds are produced and dispersed

Fruits
* No fruits

Application: Recognition features of bryophyte, filicinophyta, coniferophyta, and angiospermophyta.

Question 61

Outline the characteristics of the angiospermophyta.

5.3

Answer 61

Vegetative organs - parts of the plant concerned with growth rather than reproduction
* Roots, stems and leaves are usually present

Vascular tissue
* Xylem and phloem are both present

Cambium - cells between xylem and phloem that can produce more of these tissues
* Present

Pollen - small structures containing male gametes that are dispersed
* Pollen is produced in male cones

Ovules - contains a female gamete and develops into a seed after fertilization
* Ovules are produced in female cones

Seeds - dispersible unit consisting of an embryo plant and food reserves
* Seeds are produced and dispersed

Fruits
* Fruits are produced

Application: Recognition features of bryophyte, filicinophyta, coniferophyta, and angiospermophyta.

Question 62

State seven major animal phyla.

5.3

Answer 62

Porifera
Cnidarian
Platyhelminthes
Annelida
Mollusca
Arthropoda
Chordata

Application: Recognition features of porifera, cnidarian platyhelminthes, annelida, mollusca, arthropoda and chordata.

Question 63

Outline the characteristics of the phylum porifera.

5.3

Answer 63

Examples:
* sponges

Mouth/anus
* No mouth or anus

Symmetry
* None

Skeleton
* Internal spicules (sketetal needles)

Other
* Many pores over the surface

Application: Recognition features of porifera, cnidarian platyhelminthes, annelida, mollusca, arthropoda and chordata.

Question 64

Outline the characteristics of the phylum cnidaria.

5.3

Answer 64

Examples:
* hydras, jellyfish, corals, sea anemones

Mouth/anus
* Mouth only

Symmetry
* Radial

Skeleton
* Soft, but hard corals secrete CaCO3

Other
* Tentacles arranged in rings around the mouth

Application: Recognition features of porifera, cnidarian platyhelminthes, annelida, mollusca, arthropoda and chordata.

Question 65

Outline the characteristics of the phylum platyhelminthes.

5.3

Answer 65

Examples:
* flatworms, fukes, tapeworms

Mouth/anus
* Mouth only

Symmetry
* Bilateral

Skeleton
* Soft, with no skeleton

Other
* Flat and thin bodies in the shape of a ribbon.

Application: Recognition features of porifera, cnidarian platyhelminthes, annelida, mollusca, arthropoda and chordata.

Question 66

Outline the characteristics of the phylum mollusca.

5.3

Answer 66

Examples:
* bivalves, gastropods, snails, chitons, squid, octopus

Mouth/anus
* Mouth and anus

Symmetry
* Bilateral

Skeleton
* Most have shell made of CaCO3

Other
* **A fold in the body wall called the mantle secretes the shell. **

Application: Recognition features of porifera, cnidarian platyhelminthes, annelida, mollusca, arthropoda and chordata.

Question 67

Outline the characteristics of the phylum annelida.

5.3

Answer 67

Examples:
* marine bristleworms, oligochaetes, leeches

Mouth/anus
* Mouth and anus

Symmetry
* Bilateral

Skeleton
* Internal cavity with fluid under pressure

Other
* Very segmented

Application: Recognition features of porifera, cnidarian platyhelminthes, annelida, mollusca, arthropoda and chordata.

Question 68

Outline the characteristics of the phylum arthropoda.

5.3

Answer 68

Examples:
* ** insects, arachnids, crustaceans, myriapods**

Mouth/anus
* Mouth and anus

Symmetry
* Bilateral

Skeleton
* External skeleton made of plates of chitin

Other
* **Segmented bodies and legs or other appendages with joints between the sections **

Application: Recognition features of porifera, cnidarian platyhelminthes, annelida, mollusca, arthropoda and chordata.

Question 69

Define “vertebrate” as related to classification of chordata.

5.3

Answer 69

The vertebrate animals are all the members of the phylum chordata that possess a backbone that runs from head to tail and surrounds and protects the main nerve cord. In vertebrates the notochord becomes part of the back bone during embryonic development.

Application: Recognition of features of birds, mammals, amphibians, reptiles and fish.​

Question 70

State the major classes of chordata.

5.3

Answer 70

• birds
• mammals
• amphibians
• reptiles
• fish

Application: Recognition of features of birds, mammals, amphibians, reptiles and fish.​

Question 71

Outline the characteristics of fish.

5.3

Answer 71

Body covering
* Scales

Reproduction
* External

Breathing
* Gills

Limbs
* No limbs

Temperature
* Do not maintain constant body temperature

Other
* Have swim bladder

Application: Recognition of features of birds, mammals, amphibians, reptiles and fish.​

Question 72

Outline the characteristics of amphibians.

5.3

Answer 72

Body covering
* Soft moist skin permeable to water and gases

Reproduction
* External

Breathing
* Simple lungs with small folds and moist skin for gas exchange

Limbs
* Pentadactyl limbs (4)

Temperature
* Do not maintain constant body temperature

Other
* Larval stage in water; adult on land

Application: Recognition of features of birds, mammals, amphibians, reptiles and fish.​

Question 73

Outline the characteristics of reptiles.

5.3

Answer 73

Body covering
* Impermeable skin covered in scales

Reproduction
* Internal (soft eggs)

Breathing
* Lungs with extensive folding

Limbs
* Pentadactyl limbs (4)

Temperature
* Do not maintain constant body temperature

Other
* Simple teeth with no living tissue

Application: Recognition of features of birds, mammals, amphibians, reptiles and fish.​

Question 74

Outline the characteristics of birds.

5.3

Answer 74

Body covering
* Skin with feathers

Reproduction
* Internal (hard eggs)

Breathing
* Lungs with para-bronchial tubes

Limbs
* Pentadactyl limbs (4)

Temperature
* Maintain constant body temperature

Other
* Wings, beaks but no teeth

Application: Recognition of features of birds, mammals, amphibians, reptiles and fish.​

Question 75

Outline the characteristics of mammals.

5.3

Answer 75

Body covering
* Hairs

Reproduction
* Internal

Breathing
* Lungs with alveoli

Limbs
* Pentadactyl limbs (4)

Temperature
* Maintain constant body temperature

Other
* Most give birth to live young and all feed young with milk from mammary glands

Application: Recognition of features of birds, mammals, amphibians, reptiles and fish.​

Question 76

Define “dichotomous key.”

5.3

Answer 76

A dichotomous key is a tool for identification of unknown organisms. Sets of statements act as clues leading to the identification of an organism or group.

Skill: Construction of dichotomous keys for use in identifying specimens.

Question 77

Define “clade.”

5.4

Answer 77

A clade is a group of organisms that have evolved from a common ancestor.

Understanding: A clade is a group of organisms that have evolved from a common ancestor.

Question 78

Explain how the base sequence of a gene or the corresponding amino acid sequence of a protein can provide evidence for which species are part of a clade.

5.4

Answer 78

• All organisms use DNA and RNA as genetic material and the genetic code by which proteins are synthesised is (almost) universal.
• The number of differences between comparable base sequences demonstrates the degree of evolutionary divergence
• A greater number of differences between comparable base sequences suggests more time has past since two species diverged
• Hence, the more similar the base sequences of two species are, the more closely related the two species are expected to be

Understanding: Evidence for which species are part of a clade can be obtained from the base sequences of a gene or the corresponding amino acid sequence of a protein.

Question 79

Outline the use of a “molecular clock” to determine time since divergence between two species.

5.4

Answer 79

• Differences in the base sequence of DNA and therefore in the amino acid sequence of proteins are the result of mutations.
• They accumulate gradually over long periods of time.
• There is evidence that mutations occur at a roughly constant rate so they can be used as a molecular clock.
• The number of differences in sequence can be used to deduce how long ago species split from a common ancestor.

Understanding: Sequence differences accumulate gradually so there is a positive correlation between the number of differences between two species and the time since they diverged from a common ancestor.​

Question 80

Define “homologous structure.”

5.4

Answer 80

Homologous structures are similar because of similar ancestry; for example the chicken wing, human arm and other pentadactyl forelimbs.

Understanding: Traits can be analogous or homologous.

Question 81

Define “analogous structure.”

5.4

Answer 81

Analogous structures are similar because of convergent evolution. The human eye and the octopus eye show similarities in structure and function but they are analogous because they evolved independently.Homologous structures are similar because of similar ancestry; for example the chicken wing, human arm and other pentadactyl forelimbs.

Understanding: Traits can be analogous or homologous.

Question 82

Define “cladogram.”

5.4

Answer 82

**A cladogram is a tree diagram based on similarities and differences between the species in a clade. **Cladograms are almost always now based on base
or amino acid sequences.

**The branching points on cladograms are called nodes. **The node represents a hypothetical ancestral species that split to form two or more species.

Understanding: Cladograms are tree diagrams that show the most probable sequence of divergence in clades.​

Question 83

Outline the role of technological advancements in the reclassification of some groups.

5.4

Answer 83

• DNA and protein sequencing can provide more information on evolutionary relationships than morphology can
• As a result, some groups have been reclassified: merged, divided, organisms have been transferred

Understanding: Evidence from cladistics has shown that classifications of some groups based on structure did not correspond with the evolutionary origins of a group or species.​

Question 84

Outline the reason and evidence for the reclassification of the figwort family.

5.4

Answer 84

Evidence from cladistics has shown thatclassifcations of
some groups based on structure did not correspond with
the evolutionary origins of a group of species. Cladograms showed that species in the family did not
all share a recent common ancestor.

Application: Reclassification of the figwort family using evidence from cladistics.

Question 85

Outline primate cladograms.

5.4

Answer 85

The closest relatives of humans are chimpanzees and bonobos. The entire genome ofthese three species has been sequenced giving very strong evidence for the construction of a cladogram.

Application: Cladograms including humans and other primates.