Topic 5: Evolution and Biodiversity

Question 1

What is evolution?

Answer 1

A change in the allele frequency of a population’s gene pool over successive generations

Question 2

What are fossils?

Answer 2

A fossil is the preserved remains or traces of any organism from the remote past

Preserved remains (body fossils) provide direct evidence of ancestral forms and include bones, teeth, shells, leaves, etc.

Traces provide indirect evidence of ancestral forms and include footprints, tooth marks, burrows and faeces (coprolite)

Question 3

What is the fossil record?

Answer 3

The totality of fossils, both discovered and undiscovered, is referred to as the fossil record

The fossil record shows that over time changes have occurred in the features of living organisms (evolution)

Question 4

What is the law of fossil succession?

Answer 4

Fossils can be dated by determining the age of the rock layer (strata) in which the fossil is found

Sedimentary rock layers develop in a chronological order, such that lower layers are older and newer strata form on top
Each strata represents a variable length of time that is classified according to a geological time scale (eons, eras, periods)

Question 5

What order are organisms found in rocks/fossils?

Answer 5

Prokaryotes appear in the fossil record before eukaryotes

Ferns appear in the fossil record before flowering plants

Invertebrates appear in the fossil record before vertebrate species

Question 6

What are transitional fossils?

Answer 6

A fossil that shows an intermediate state between an ancestral trait and that of its later descendants.

They establish the links between species by exhibiting traits common to both an ancestor and its predicted descendents

An example of a transitional fossil is archaeopteryx, which links the evolution of dinosaurs (jaws, claws) to birds (feathers)

As new fossils are discovered, new evolutionary patterns are emerging and old assumptions are challenged

Question 7

Example of fossil evidence:

Answer 7

how humans evolved

Question 8

What is selective breeding and how is it an evidence of evolution?

Answer 8

a form of artificial selection, whereby man intervenes in the breeding of species to produce desired traits in offspring

By breeding members of a species with a desired trait, the trait’s frequency becomes more common in successive generations

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

Question 9

What is comparative anatomy and how is it evidence of evolution?

Answer 9

Comparative anatomy of groups of organisms may show certain structural features that are similar, implying common ancestry

Anatomical features that are similar in basic structure despite being used in different ways are called homologous structures

The more similar the homologous structures between two species are, the more closely related they are likely to be

Question 10

Homologous structure

Answer 10

Look superficially different and perform different functions but are similar in structure. E.g. pentadactyl limb. Same origin but have diverged due to use/function. Adaptive radiation.

Question 11

Analogous structure

Answer 11

different origins but have diverged due to the performance of a similar function. Convergent evolution.

Question 12

Vestigial structures

Answer 12

structures that have no function and have slowly diminished over time. Appendix; pelvic bone in whales.

Question 13

What is speciation and how is it evidence of evolution?

Answer 13

Populations of a species can gradually diverge into separate species by
evolution.
● The characteristics of the two populations will gradually diverge to the
extent where they will no longer be able to interbreed to produce fertile
offspring.
● Endemic species: one found only in a certain geographical area. Occurs by
migration and subsequent divergence.

Question 14

evolution example?

Answer 14

Industrial melanism:
● Dark varieties of light insects are called melanistic.
● Biston Betularia, peppered moth.
● Melanic moths are better camouflaged in polluted areas as sulphur dioxide blackens bark of trees and kills light coloured lichens.
● Example of evolution by natural selection as melanism affects survival
rates.

Question 15

What is natural selection and who invented this theory?

Answer 15

The theory of natural selection was posited by Charles Darwin (and also Alfred Wallace) who described it as ‘survival of the fittest’

According to this theory, it is not necessarily the strongest or most intelligent that survives, but the ones most responsive to change

Question 16

Natural selection mnemonic: ICEAGE

Answer 16

Inherited variation: exists within the population

Competition: results from an overproduction of offspring

Environmental: pressures lead to differential reproduction

Adaptations: which benefit survival are selected for

Genotype: frequency changes across generations

Evolution: occurs within the population

Question 17

How does variation effect natural selection?

Answer 17

● Natural selection occurs when variation amongst members of the same species occurs.

● This way specific characteristics can be favoured over others, resulting in
higher chances of those characteristics becoming predominant in a gene
pool.

Question 18

What are 3 sources of variation?

Answer 18

● Mutation: base-shift or base substitution. Produces new alleles, due to base substitution at SNPs, enlarging the gene pool.

● Meiosis: New combination of alleles by breaking up existing combinations. Every new cell created by meiosis is likely to carry a different combination of alleles. Crossing over (recombination),
independent orientation.

● Sexual reproduction. Gametes come from different parents – combination
of alleles from two individuals. Allows mutations in different individuals
to be brought together.

Question 19

What is the Malthusian dilemma?

Answer 19

populations multiply geometrically (i.e. exponential progression), while food resources only increase arithmetically (i.e. linear progression)

In other words, species tend to produce more offspring than the environment can sustainably support

If left to follow course, a stable population will inevitably outgrow its resource base, leading to competition for survival

Question 20

What are adaptations?

Answer 20

● Characteristics that make an individual suited to its environment.
● These occur over time by natural selection.
● Acquired characteristics develop during the lifetime of an individual but
these are considered to be non-inheritable.

Question 21

5 types of adaptations?

Answer 21

Structural: Physical differences in biological structure (e.g. neck length of a giraffe)

Behavioural: Differences in patterns of activity (e.g. opossums feigning death when threatened)

Physiological: Variations in detection and response by vital organs (e.g. homeothermy, colour perception)

Biochemical: Differences in molecular composition of cells and enzyme functions (e.g. blood groups, lactose tolerance)

Developmental: Variable changes that occur across the life span of an organism (e.g. patterns of ageing / senescence)

Question 22

How is allele frequency an example of variation? Types of alleles:

Answer 22

The variation that exists within a population is heritable (i.e. genetic) and determined by the presence of alleles

These alleles may be passed from parent to offspring via sexual reproduction.
1. Beneficial alleles will better equip the organism to survive and hence produce more offspring (encodes beneficial adaptations)
2. Detrimental alleles will harm the survival prospects of an organism, leading to fewer viable offspring
3. Neutral alleles will not affect the organisms survival prospects

Question 23

What is adaptive radiation?

Answer 23

describes the rapid evolutionary diversification of a single ancestral line:
-It occurs when members of a single species occupy a variety of distinct niches with different environmental conditions
-Consequently, members evolve different morphological features (adaptations) in response to the different selection pressures

Question 24

example of adaptive radiation?

Answer 24

Daphne Major is a volcanic island that forms part of the archipelago that is collectively referred to as the Galapagos Islands

It is the native habitat of a variety of bird species known as Darwin’s finches (subfamily: Geospizinae)

Darwin’s finches demonstrate adaptive radiation and show marked variation in beak size and shape according to diet

Finches that feed on seeds possess compact, powerful beaks – with larger beaks better equipped to crack larger seed cases

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

Question 25

Causes and process of antibiotic resistance:

Answer 25

CAUSES o Widespread use of antibiotics. o Bacteria reproduce rapidly. o Large populations of bacteria mean higher chance of gene mutation forming resistance. o Bacteria can pass genes between each other laterally using plasmids. PROCESS o Resistance gene either formed by mutation or received by another bacterium. o Use of antibiotic provides environment for natural selection to occur (it is a selection pressure). o Bacteria with resistance survive and reproduce rapidly forming more resistant organisms in the population. This is why high risk patients are given a cocktail of antibiotics - to kill off the bacteria that become resistant to one type of antibiotic with another antibiotic.

Question 26

What is the binomial system of classification

Answer 26

Genus species: o Genus name, upper case. o Species name, lower case. ● Can be abbreviated to G. species after first use. (e.g. Homo sapiens)

Question 27

What are the 3 domains that living organisms are classified into:

Answer 27

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.)

Question 28

What are the hierarchy of taxa?

Answer 28

katy perry comes over for grape soda Kingdom Phylum Class Order Family Genus Species

Question 29

2 Types of Classification:

Answer 29

Natural classification: ● All members of a genus or higher taxon should have a common ancestor. ● This is called natural classification. ● Natural groups share many characteristics. Advantages of natural classification: ● Identification of species is easier. Dichotomous keys can be used to help with this process. They can be assigned to a specific kingdom, phylum class, etc. and therefore be identified relative to other known species. ● Because all of the members of a group in a natural classification have evolved from a common ancestral species, they inherit common characteristics. This allows prediction of characteristic within a group. A disadvantage of natural classifications is that because they predict evolutionary relationships, they change with new information vs Artificial classification involves arbitrarily selecting unifying characteristics first and then grouping organisms accordingly The advantage of artificial classification is that such schemes are easy to develop and relatively stable (unlikely to change) The disadvantage is that they do not generally show evolutionary relationships and for this reason are not commonly used -For example, if organisms were classified according to the presence of fins then whales would be grouped with fish -If organisms were classified based on the presence of shells then snails would be grouped with turtles and not with squid

Question 30

4 Types of plant phyla

Answer 30

Bryophyta -Has no vascularisation (i.e. lacks xylem and phloem) -Has no ‘true’ leaves, roots or stems (are anchored by a root-like structure called a rhizoid) -Reproduce by releasing spores from sporangia (reproductive stalks) Examples include mosses and liverworts Filicinophyta -Has vascularisation (i.e xylem and phloem) -Have leaves, roots and stems (leaves are pinnate – consisting of large fronds divided into leaflets) -Reproduce by releasing spores from clusters called sori on the underside of the leaves Examples include ferns Coniferophyta -Has vascularisation -Have leaves, roots and stems (stems are woody and leaves are waxy and needle-like) -Reproduce by non-motile gametes (seeds) which are found in cones Examples include pine trees and conifers Angiospermophyta -Has vascularisation -Have leaves, roots and stems (individual species may be highly variable in structure) -Reproduce by seeds produced in ovules within flowers (seeds may develop in fruits) Examples include all flowering plants and grasses

Question 31

7 types of animal phyla:

Answer 31

Porifera -No body symmetry (asymmetrical) -No mouth or anus (have pores to facilitate the circulation of material) -May have silica or calcium carbonate based spicules for structural support Examples include sea sponges Cnidaria -Have radial symmetry -Have a mouth but no anus (single entrance body cavity) -May have tentacles with stinging cells for capturing and disabling prey Examples include jellyfish, sea anemones and coral Platyhelmintha -Have bilateral symmetry -Have a mouth but no anus (single entrance body cavity) -Have a flattened body shape to increase SA:Vol ratio and may be parasitic Examples include tapeworms and planaria Annelida -Have bilateral symmetry -Have a separate mouth and anus -Body composed of ringed segments with specialisation of segments Examples include earthworms and leeches Mollusca -Have bilaterial symmetry -Have a separate mouth and anus -Body composed of a visceral mass, a muscular foot and a mantle (may produce shell) Examples include snails, slugs, octopi, squid and bivalves (e.g. clams) Arthropoda -Have bilateral symmetry -Have a separate mouth and anus -Have jointed body sections / appendages and have a hard exoskeleton (chitin) Examples include insects, crustaceans, spiders, scorpions and centipedes Chordata -Have bilateral symmetry -Have a separate mouth and anus -Have a notochord and a hollow, dorsal nerve tube for at least some period of their life cycle Examples include mammals, birds, reptiles, amphibians and fish (also invertebrate sea squirts)

Question 32

What are the 5 classes of vertebrate:

Answer 32

Fish -Covered in scales made out of bony plates in the skin -Reproduce via external fertilisation (egg and sperm released into the environment) -Breathe through gills that are covered with an operculum -Does not maintain a constant internal body temperature (ectothermic) Amphibian -Moist skin, permeable to gases and water -Reproduce via external fertilisation (usually spend larval state in water, adult state on land) -Can breathe through skin but also possess simple lungs -Do not maintain a constant internal body temperature (ectothermic) Reptiles -Covered in scales made out of keratin -Reproduce via internal fertilisation and females lay eggs with soft shells -Breathe through lungs that have extensive folding (increases SA:Vol ratio) -Do not maintain a constant internal body temperature (ectothermic) Birds -Covered in feathers (made out of keratin) -Reproduce via internal fertilisation and females lay eggs with hard shells -Breathe through lungs with parabronchial tubes -Maintain a constant internal body temperature (endothermic) Mammals -Skin has follicles which produce hair made out of keratin -Reproduce via internal fertilisation and females feed young with milk from mammary glands -Breathe through lungs with alveoli -Maintain a constant internal body temperature (endothermic)

Question 33

What is a dichotomous key?

Answer 33

a method of identification whereby groups of organisms are divided into two categories repeatedly: -With each sequential division, more information is revealed about the specific features of a particular organism -When the organism no longer shares its totality of selected characteristics with any organism, it has been identified