IB Biology HL

Combined Syndey Wong's quizlets

convergent evolution

process by which unrelated organisms independently evolve similarities when adapting to similar environments

analogous structures

similarities among unrelated species that result from convergent evolution

homologous structures

similar structures that related species have inherited from a common ancestor

adaptive radiation

an evolutionary pattern in which many species evolve from a single ancestral species

divergent evolution

when two or more species sharing a common ancestor become more different over time; occurs as a result of adaptive radiation

heritable

a genetic trait which can be passed on to offspring

theory of evolution by natural selection

idea that the frequency of characteristics in a population changes due to the survival advantage they give an individual that has those traits

evolution

cumulative change in the heritable characteristics of a population

fossils

petrified remains of plants or animals

selective breeding

choosing organisms with particular traits to reproduce so that their offspring share these traits

artificial selection

selective breeding for particular traits

pentadactyl limb

an arm or leg with five jointed digits

speciation

process by which one species splits into two species which can no longer interbreed

hybrid

something that has the properties of two things

punctuated equilibrium

evolution by big jumps with periods of no change in between

gradualism

evolution by slow, continuous small changes

melanism

dark colouring

polymorphism

having several different forms

industrial melanism

production of dark-coloured form of organism, well camouflaged in areas polluted with soot

morphology

the structure and shape of an organism

plasmid transfer

a technique used by bacteria to share DNA

taxa

a level in the hierarchy of classifying living organisms, e.g. kingdom

phylum

a taxon made up of many classes

kingdom

a taxon made up of many phyla

families

a group of related genera

genus

a group of species with shared characteristics

radial symmetry

body plan where any line through the centre of the organism produces two similar halves, e.g. sea anemone

bilateral symmetry

one side of an organism is a mirror image of the other side

segmentation

having separate parts that are joined together

ectothermic

cold blooded, constant body temperature not maintained

endothermic

warm blooded, body maintained at a constant temperature

cladistics

the study of evolutionary relationships

primitive traits

ancient traits observed in the earliest common ancestor, also called plesiomorphic traits

plesiomorphic traits

ancient traits observed in the earliest common ancestor, also called primitive traits

ancestral trait

a characteristic inherited from an ancestor

apomorphic or derived traits

characteristics that have evolved fairly recently

molecular systematics

classifying organisms by genetic sequences or protein sequences

degenerate code

more than one codon coding for a given amino acid

analogous traits

two traits are analogous if they have similar functions but dissimilar ancestries, for example, insect wings and bird wings

cladogram

branching diagram showing relationships amongst a group of organisms

node

point in a cladogram where lines meet at a common ancestor showing a speciation event

sister groups

groups in a cladogram that are closely related, with a recent common ancestor

outgroup

a group that is not closely related to others

parsimony

the principle by which the simplest and least convoluted explanation is chosen

bipedalism

ability to walk on two legs

aestivation

the arrangement of flower petals within a bud

internal transcribed spacer

a marker in DNA used to check similarities between species

monophyletic

having one common ancestor

polyphyletic

said of two or more clades that have different common ancestors

paraphyletic

a group containing some but not all of the descendants of a common ancestor

transitional fossils

fossils that show links in traits between groups of organisms used to document intermediate stages in the evolution of a species.

5.1 Define evolution.

• Evolution occurs when heritable characteristics of a species change.

(cumulative) change in heritable/genetic characteristics of a population;new species arise from pre-existing species;change/adaptation of a population due to natural selection / descent with modification;

5.1 Discuss the evidence regarding the theory of evolution.

• The fossil record provides evidence for evolution.

-fossils are traces of parts of organisms (bones or leaf imprints) or their activities (footprints or burrows) left in layers of rock.

-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

-the ordered succession of fossils suggests that newer species likely evolved as a result of changes to ancestral species

**fossil record is incomplete

-fossilisation requires an unusual set of specific circumstances in order to occur, so very few organisms become fossils

-only the hard parts of an organism are typically preserved, so only fragments of remains are discovered

-with limited fossil data, it can be difficult to discern the evolutionary patterns that result from ancestral forms ('missing links')

-transitional fossils demonstrate the intermediary forms that occurred over the evolutionary pathway taken by a single genus

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

-e.g. 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

5.1 Explain selective breeding and what it shows regarding natural selection.

• Selective breeding of domesticated animals shows that artificial selection can cause evolution.

-selective breeding is 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

-selective breeding of plant crops has allowed for the generation of new types of foods from the same ancestral plant source

-e.g. plants of the genus Brassica have been bred to produce different foods by modifying plant sections through artificial selection

-e.g. broccoli (modified flower buds), cabbage (modified leaf buds) and kale (modified leaves)

-selective breeding of domesticated animals has also resulted in the generation of diverse breeds of offspring

-e.g. dog breeding

5.1 Explain the evolution of homologous structures.

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

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

-homologous structures: anatomical features that are similar in basic structure despite being used in different ways

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

-homologous structures illustrate adaptive radiation, whereby several new species rapidly diversify from an ancestral source, with each new species adapted to utilise a specific unoccupied niche

• Application: Comparison of the pentadactyl limb of mammals, birds, amphibians & reptiles with different modes of locomotion

-a classical example of homologous structures is the pentadactyl limb in a variety of different animals

-mammals, birds, amphibians and reptiles all share a similar arrangement of bones in their appendages based on a five-digit limb

-despite possessing similar bone arrangements, animal limbs may be highly dissimilar according to the mode of locomotion:

-human hands are adapted for tool manipulation (power vs precision grip)

-bird and bat wings are adapted for flying

-horse hooves are adapted for galloping

-whale and dolphin fins are adapted for swimming

5.1 Explain speciation.

• Populations of a species can gradually diverge into separate species via evolution

-the degree of divergence between geographically separated populations will gradually increase the longer they are separated

-as the genetic divergence between the related populations increase, their genetic compatibility consequently decreases

-eventually, the two populations will diverge to an extent where they can no longer interbreed if returned to a shared environment

-in that case, they are considered to be separate species

• Continuous variation across a geographical range of related populations matches the concept of gradual divergence

-if two populations of a species become geographically separated then they will likely experience different ecological conditions

-over time, the two populations will adapt to the different environmental conditions (due to genetic variation and natural selection) and gradually diverge from one another

-the degree of divergence will depend on the extent of geographical separation and the amount of time since separation occurred

-populations located in close proximity that separated recently will show less variation (less divergence)

-distant populations that separated a longer period of time ago will show more variation (more divergence)

5.1 Provide an example showing evolution.

• Development of melanistic insects in polluted areas

-peppered moths (Biston betularia) exist in two distinct polymorphic forms - a light colouration and a darker melanic variant

-unpolluted environment: the trees are covered by a pale-coloured lichen, which provides camouflage for the lighter moth

-polluted environment: sulphur dioxide kills the lichen while soot blackens the bark, providing camouflage for the dark moth

-frequency of the two different forms of peppered moth is dependent on the environment and evolves as conditions change

-before the industrial revolution, the environment was largely unpolluted and the lighter moth had a survival advantage

-following the industrial revolution, the environment became heavily polluted, conferring a survival advantage to the darker moth

5.2 Explain natural selection.

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

• Mutation, meiosis and sexual reproduction causes variation between individuals in a species

mutations: changing the genetic composition of gametes (germline mutation) leads to changed characteristics in offspring

meiosis: via either crossing over (prophase I) or independent assortment (metaphase I)

sexual reproduction: the combination of genetic material from two distinct sources creates new gene combinations in offspring

• 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.

-according to the theory of natural selection, it is not necessarily the strongest or most intelligent that survives, but the ones most responsive to change

The process of natural selection occurs in response to a number of conditions:

1) inherited variation: there is genetic variation within a population which can be inherited

2) competition: there is a struggle for survival (species tend to produce more offspring than the environment can support)

3) selection: environmental pressures lead to differential reproduction within a population

4) adaptations: individuals with beneficial traits will be more likely to survive and pass these traits on to their offspring

5) evolution: over time, there is a change in allele frequency within the population gene pool

5.2 Explain the reason for overproduction.

• Species tend to produce more offspring than the environment can support

-a stable population will inevitably outgrow its resource base, leading to competition for survival

-with more offspring, there are less resources available to other members of the population (environmental resistance)

-this will lead to a struggle for survival and an increase in the mortality rate (causing population growth to slow and plateau)

-this concept is central to Darwin's understanding of 'survival of the fittest' - any trait that is beneficial for competitive survival will be more likely to be passed on to offspring according to natural selection

5.2 Define adaptations.

• Adaptations are characteristics that make an individual suited to its environment and way of life

5.2 Explain the role of adaptations in natural selection.

• Individuals that reproduce pass on characteristics to their offspring

These adaptations may be classified in a number of different ways:

-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)

Biological adaptations have a genetic basis (i.e. encoded by genes) and may be passed to offspring when the parents reproduce

-organisms with beneficial adaptations will be more likely to survive long enough to reproduce and pass on these genes

-organisms without these beneficial adaptations will be less likely to survive long enough to reproduce and pass on their genes

Hence adaptations result in differential reproduction within a species, allowing for natural selection to occur

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

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

-alleles may be passed from parent to offspring via sexual reproduction

-alleles encode for the phenotypic polymorphisms of a particular trait and may be beneficial, detrimental or neutral:

-due to natural selection, the proportion of different alleles will change across generations (evolution)

-as beneficial alleles improve reproductive prospects (more offspring), they are more likely to be passed on to future generations

-conversely, detrimental alleles result in fewer offspring and hence are less likely to be present in future generations

-when environmental conditions change, what constitutes a beneficial or detrimental trait may change, and thus the allele frequencies in a population are constantly evolving

5.2 Application: Explain the changes in beaks of finches on Daphne Major.

adaptive radiation: the rapid evolutionary diversification of a single ancestral line

-occurs when members of a single species occupy a variety of distinct niches with different environmental conditions

-members evolve different morphological features (adaptations) in response to the different selection pressures

e.g. the variety of beak types seen in the finches of the Galapagos Islands

-the finches have specialised beak shapes depending on their primary source of nutrition (e.g. seeds, insects, nuts, nectar)

Daphne Major

-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

-finches with larger beaks were better equipped to feed on the seeds and thus produced more offspring with larger beaks

5.2 Application: Explain the evolution of antibiotic resistance in bacteria.

a. antibiotics (are chemicals) used to treat bacterial diseases;

b. within populations, bacteria vary in their (genetic) resistance to antibiotics/fitness;

c. resistance arises by (random) gene mutation;

d. when antibiotics are used antibiotic-sensitive bacteria are killed;

e. (natural) selection favours those with resistance;

f. resistant bacteria survive, reproduce and spread the gene / increase allele frequency of resistant bacteria;

g. the more an antibiotic is used, the more bacterial resistance/the larger the population of antibiotic-resistant bacteria;

h. genes can be transferred to other bacteria by plasmids;

i. doctors/vets use different antibiotics but resistance develops to these as well;

j. multiple-antibiotic resistant bacteria evolve/it becomes difficult to treat some infections;

5.3 Define the binomial nomenclature of naming and explain its importance.

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

the system of nomenclature in which two terms are used to name a species of living organism, the first one indicating the genus and the second the specific epithet.

The binomial system of nomenclature provides value because:

-allows for the identification and comparison of organisms based on recognised characteristics

-allows all organisms to be named according to a globally recognised scheme

-can show how closely related organisms are, allowing for the prediction of evolutionary links

-makes it easier to collect, sort and group information about organisms

5.3 Explain when and how binomial names are given.

• When species are discovered they are given scientific names using the binomial system.

-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)

Writing conventions:

-typing the scientific name: in italics

-hand writing the scientific name: underline

5.3 Explain what taxonomists are and its principle.

• Taxonomists classify species using a hierarchy of taxa.

• The principal taxa for classifying eukaryotes are (domain comes first but its not a taxa), kingdom, phylum, class, order, family, genus and species.

-taxonomy is the science involved with classifying groups of organisms on the basis of shared characteristics

-organisms are grouped according to a series of hierarchical taxa - the more taxa organisms share, the more similar they are

• All organisms are classified into three domains

-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.)

**members of these domains should be referred to as archaeans, bacteria and eukaryotes.

-original evidence for this came from base sequences of ribosomal RNA

-these sequences are found in all organisms and evolves slowly, so it is suitable for studying the earliest evolutionary events.

-the sequences suggests that prokaryotes diverged into Eubacteria and Archaea early in the evolution of life

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

Animal example: Humans

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Primates

Family: Hominidae

Genus: Homo

Species: Sapiens

Plant example: Garlic

Kingdom: Plantae

Phylum: Magnoliophyta

Class: Liliopsida

Order: Asparagales

Family: Amaryllidaceae

Genus: Allium

Species: sativum

5.3 Explain what natural classifications are, and what it indicates.

-natural classification involves grouping organisms based on similarities first and then identifying shared characteristics

• Natural classifications help in identification of species and allow the prediction of characteristics shared by species within a group

-all members of a particular group would have shared a common ancestor

-can be used to predict characteristics shared by species within a group

**they are highly mutable and tend to change as new information is discovered

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

-identifies traits based on groupings, rather than assigning groups based on traits

-can be used to show evolutionary relationships and predict characteristics shared by species within a group

-each taxonomic level includes all species that would have evolved from a common ancestor

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

**because they predict evolutionary relationships, they change with new information

-groups of species may be separated into different genera if new evidence suggests they evolved from different ancestral species

-different species may be grouped into a shared taxon if new evidence suggests more recent common ancestry

-e.g Homininae sub-family was created to include gorillas and chimpanzees when it was deduced that they share more common ancestry with humans than with other great apes (e.g. orang-utan)

5.3 Application: Recognition features of bryophyta, filicinophyta, coniferophyta and angiospermophyta

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 vascular tissues (i.e xylem and phloem)

All 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

5.3 Application: Recognition features of porifera, cnidaria, platyhelmintha, annelida, mollusca, arthropoda and chordata

invertebrates: porifera, cnidaria, platyhelmintha, annelida, mollusca and arthropoda

**most vertebrates are in chordata (but not all!)

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 appendages

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)

5.3 Application: Recognition of vertebrate classes.

• Recognition features of birds, mammals, amphibians, reptiles and fish.

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 with one gill slit

Does not maintain a constant internal body temperature (ectothermic)

No limbs.

Fins supported by rays.

Remain in water throughout their life cycle.

Swim bladder containing gas for buoyancy.

Amphibian

Moist skin, permeable to gases and water

Reproduce via external fertilisation

Larval stage that lives in water and adult that usually lives on land.

Can breathe through skin but also possess simple lungs

Simple lungs with small folds and moist skin for gas exchange.

Do not maintain a constant internal body temperature (ectothermic)

Tetrapods with pentadactyl limbs.

Four legs when adult.

Eggs coated in protective jelly.

Reptiles

Impermeable skin 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)

Tetrapods with pentadactyl limbs.

Four legs (in most species).

Sperm passed into the female for internal fertilization.

Female lays eggs with soft shells.

Teeth al of one type, with no living parts.

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, ventilated using air sacs.

Maintain a constant internal body temperature (endothermic)

Tetrapods with pentadactyl limbs.

Two legs and two wings.

Beak but no teeth.

Mammals

Skin has follicles which produce hair made out of keratin

Reproduce via internal fertilisation and females feed young with milk from mammary glands

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

Breathe through lungs with alveoli, ventilated using ribs and a diaphragm.

Maintain a constant internal body temperature (endothermic)

Tetrapods with pentadactyl limbs.

Four legs in most (or two legs and two wings/arms. .

Teeth of different types with a living core.

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

dichotomous key: method of identification whereby groups of organisms are divided into two categories repeatedly

Look into notes!

5.4 Define a clade, cladogram and

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

• Cladograms are tree diagrams that show the most probable sequence of divergence in clades.

Cladistics: a method of classification of animals and plants that aims to identify and take account of only those shared characteristics (which can be deduced to have originated in the common ancestor of a group of species during evolution, not those arising by convergence)

5.4 Application: Cladograms including humans and other primates.

Look into notes.

According to a cladogram outlining the evolutionary history of humans and other primates:

-humans, chimpanzees, gorillas, orangutans and gibbons all belong to a common clade - the

Hominoids

-the Hominoid clade forms part of a larger clade - the Anthropoids - which includes Old World and New World monkeys

**from left to right

-lorises, pottos, and lemurs

-tarsiers

-new world monkeys

-old world monkeys

-gibbons

-orangutans

-gorillas

-chimpanzees

-humans

5.4 Explain why structural evidence is not used to construct cladistics.

• Evidence from cladistics has shown that classification of some groups based on structure did not correspond

with the evolutionary origins of a group or species

there are two key limitations to using morphological differences as a basis for classification:

-closely related organisms can exhibit very different structural features due to adaptive radiation (e.g. pentadactyl limb)

-distantly related organisms can display very similar structural features due to convergent evolution

**it may occur when different species occupy the same habitat and are thus subjected to the same selection pressures

• Traits can be analogous or homologous

-structural traits are not commonly used to determine clades as such features may not necessarily indicate shared heritage

homologous structures: traits that are similar because they are derived from common ancestry

analogous structures: traits that are superficially similar but were derived through separate evolutionary pathways

-using molecular evidence, scientists have discovered that many species thought to be closely related based on shared structural characteristics actually demonstrate distinct evolutionary origins

e.g. crocodiles have been shown to be more closely related to birds than lizards, despite closely resembling lizards in structure

5.4 Explain the current method of constructing cladistics.

• Evidence for which species are part of a clade can be obtained from the base sequence of a gene or the

corresponding amino acid sequence of a protein.

Molecular evidence is used because:

-all organisms use DNA and RNA as genetic material and the genetic code by which proteins are synthesised is (almost) universal

-so have shared molecular heritage

-base and amino acid sequences can be compared to ascertain levels of relatedness

-over the course of millions of years, mutations will accumulate within any given segment of DNA

-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

When comparing molecular sequences, scientists may use non-coding DNA, gene sequences or amino acid sequences:

-non-coding DNA provides the best means of comparison as mutations will occur more readily in these sequences

-gene sequences mutate at a slower rate, as changes to base sequence may potentially affect protein structure and function

-amino acid sequences may also be used for comparison, but will have the slowest rate of change due to codon degeneracy

-amino acid sequences are typically used to compare distantly related species (i.e. different taxa)

-DNA or RNA base sequences are often used to compare closely related organisms (e.g. different haplogroups - such as various human ethnic groups)

**a comparison of amino acid sequences is not as accurate as a DNA comparison. Changes at the DNA level need not always result in a different protein. (Remember the genetic code!)

• 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

-some genes or protein sequences may accumulate mutations at a relatively constant rate (e.g. 1 change per million years)

-if rate of change is reliable, scientists can calculate the time of divergence according to the number of differences

This concept is called the molecular clock and is limited by a number of factors:

-different genes or proteins may change at different rates (e.g. haemoglobin mutates more rapidly than cytochrome c)

-rate of change for a particular gene may differ between different groups of organisms

-earlier changes may be reversed by later changes, potentially confounding the accuracy of predictions

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

Until recently, figworts were the 8th largest family of flowering plants (angiosperms), containing 275 different genera

-this was problematic as many of the figwort plants were too dissimilar in structure to function as a meaningful grouping

-taxonomists examined the chloroplast gene in figworts and decided to split the figwort species into five different clades

Now less than half of the species remain in the figwort family - which is now the 36th largest among angiosperms

5.4 Skill: Analysis of cladograms to deduce evolutionary relationships.

Explain what the different features in a cladogram mean

**practice!

Constructed cladograms all typically share certain key features:

root - The initial ancestor common to all organisms within the cladogram (incoming line shows it originates from a larger clade)

nodes - Each node corresponds to a hypothetical common ancestor that speciated to give rise to two (or more) daughter taxa

outgroup - The most distantly related species in the cladogram which functions as a point of comparison and reference group

clades - A common ancestor and all of its descendants (i.e. a node and all of its connected branches)

branches -

******* update here

5.3 Distinguish between archaea and eubacteria.

Eubacteria:

-DNA with no proteins/histones

-seldom have introns

-cell walls with peptidoglycan/glycoproteins

-not in extreme environments

-different ribosome (than archaea)

Archaea:

-DNA with proteins/histones

-usually have introns

-cell walls lack peptidoglycan/glycoproteins

-found in extreme environments

-different ribosome (than eubacteria)

5.3 State the names of the three domains, giving a microbial example of each.

Eubacteria/Bacteria: E. coli / Pneumococcus / another suitable example; (scientific/common name acceptable)

Archaea: methanogens / thermophiles / another suitable example;

Eukaryota: Paramecium / yeast / another suitable example;

5.3 List out some unique characteristics of:

-mammals

-fish

-reptiles

-amphibians

-birds

5.1 Define strata and paleontology.

Strata: layers of rock or soil with characteristics that distinguish it from other layers. (strata often contain different types of fossils)

Palaeontology: the study of fossils (which provides strong evidence that life on earth has changed over time.)

5.1 Explain three pieces of evidence that fossils provide that evolution has occurred.

1: The sequence that fossils appear match the sequence in which they would be expected to evolve:

-with simple organisms in older strata and more complex organisms in more recent strata.

-(bacteria and simple algae appeared first, fungi and worms later and land vertebrates later still)

-(among the vertebrates: bony fish appeared about 420 mya, amphibians 340 mya, reptiles 320 mya, birds 250 mya and placental mammals 110 mya)

2: the sequence of fossils also fits in with the ecology of the groups

-plants fossils appearing before animal, plants on land before animals on land

-plants suitable for insect pollination before insect pollinators

3: Fossils often show transitions and/or links between living organisms and likely ancestors

5.1 Contrast analogous structures and homologous structures.

Analogous structures:

-have superficial similarities

-when studies closely are very different to each other

-had different origins

-perform the same function

Homologous structures:

-appear superficially different

-structurally similar to each other

-homologous have come from the same origin

-perform different functions.

5.1 Contrast convergent evolution and adaptive radiation.

Convergent evolution:

-when structures (of different origins) have had different origins and have become similar because they perform the same or a similar function.

Adaptive radiation:

-structures that share the same origin and have become different from each other because they perform different functions.

5.1 State an example of analogous structures and homologous structures.

Analogous:

-similarities between the tail fins of whales and fishes.

Homologous:

-the forelimbs of a human, mole, horse, porpoise and bat have the same bones, in the same relative positions

5.1 Lists the group of animals that have pentadactyl limbs.

mammals, birds, amphibians and reptiles

5.1 Define vestigial structure, and state an example.

A reduced structure that serves no function.

The appendix in humans.

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

Since populations gradually diverge over time to become separate species, then at any moment it is expected that examples of all stages of divergence can be found.

5.1 Define pentadactyl limb.

A limb with five digits

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

Human hands are adapted for tool manipulation (power vs precision grip)

Bird and bat wings are adapted for flying

Horse hooves are adapted for galloping

Whale and dolphin fins are adapted for swimming

5.2 List examples of "selective pressures."

- Competition for food

- Predation

- Parasitism

- Disease

- Competing for mates

- Competition for space

5.2 Contrast acquired characteristics with inheritable characteristics.

Inheritable characteristics are ones that can be passed on to offspring.

Acquired characteristics are not usually passed on to offspring as they are acquired during the lifetime of an individual.

**Only inherited characteristics can be acted upon by natural selection.

5.2 Outline the role of Charles Darwin and Peter and Rosemary Grant in the study of Galapagos finches.

-Darwin observed that the sizes and shapes of the beaks of the Galapagos finches varied, as did their diet.

-(Although the Finches seemed closely related they were considered separate species.

-Darwin deduced that they had come from a single population of finches on the mainland and had probably been blown to their new habitats by a storm.

-each habitat had different selection pressures leading to the finches adapting to suit the different islands, eventually leading to the formation of separate species.)

-Peter and Rosemary Grant have shown that beak characteristics and diet are closely related and when one changes, the other does also.

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

-in 1977, a drought on the island, Daphne Major caused a shortage of small seeds

-so the species of finch, G. fortis fed instead on larger, harder seeds, which the large-beaked individuals were able to crack open.

-a lot of the population died that year which highest mortality among individuals with shorter beaks.

-(In 1982-83 there was a severe El Nino event, causing eight months of heavy rain and as a result an increased supply of small, soft seeds and fewer large, hard seeds.

-G. fortis bred rapidly, in response to the increase in food availability.

-with a return to dry weather conditions and greatly reduced supplies of small seeds, breeding stopped until 1987.)

5.2 List reasons why evolution of antibiotic resistance has been rapid.

1: There has been very widespread use of antibiotics (both for treating diseases and in animal feeds used on farms)

2: Bacteria can reproduce very rapidly (with a generation time of less than an hour)

3: populations of bacteria are often huge (increasing the chance of a gene for antibiotic resistance being formed by mutation)

4: Bacteria an pass genes on to other bacteria in several ways (including using plasmids, which allow one species of bacteria to gain antibiotic resistances genes from another species)

5.2 List three trends that have been observed in the development of antibiotic resistance.

1: After an antibiotic is introduced and used on patients, bacteria showing resistance appear within a few years.

2: Resistance to the antibiotic spreads to more and more species of pathogenic bacteria.

3: In each species the proportion of infections that are caused by a resistant strain increases.

5.3 Outline the role of botanical and zoological congresses in the naming of plants and animals.

To ensure that all biologists use the same system of names for living organisms, congress attended by delegates from around the world are held at regular intervals. The first International Zoological Congress was held in Paris in 1889. It was recognised that internationally accepted rules for naming and classifying animal species were needed and these were agreed at this and subsequent congresses.

5.3 State three rules of binomial nomenclature formatting.

1. The genus begins with an upper-case letter and the species name with a lower-cases letter.

2. In typed or printed text, a binomial is shown in italics. After a binomial has been used once in a piece of text, it can be abbreviated to the initial letter of the genus name with the full species name (eg. L. borealis.)

5.3 Define taxon and taxonomist.

taxon: a taxonomic group of any rank

Taxonomist: a biologist that groups organisms into categories