Topic 5 Flashcards

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1
Q

Evolution

A
  • the process of cumulative change in heritable characteristics and/or allele frequency in the gene pool of a population over time
  • can cause populations of a species to gradually diverge into separate species
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2
Q

List the evidence for evolution.

A
  • fossil record
  • selective breeding
  • homologous structures
  • related DNA sequences
  • vestigial structures
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3
Q

Fossil record

A
  • the fossil record provides evidence for evolution
  • the sequence in which the fossils appear matches the sequence in which the organisms would be expected to evolve
  • the sequence fits with the ecology of the groups (plant before animals)
  • many sequences of fossils are known, which link together existing organisms with their likely ancestors
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4
Q

Selective breeding

A
  • proves that artificial selection can cause evolution
  • domesticated breeds were made by repeatedly selecting for and breeding the individuals most suited to human uses
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5
Q

Vestigial structures

A

reduced structures that serve little or no function; can be explained by evolution as structures that no longer have function are gradually being lost

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6
Q

Niche

A
  • the role/job a species plays in its community
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7
Q

Adaptive radiation

A
  • the diversification of a group of organisms into forms filling different ecological niches
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8
Q

Convergent evolution

A
  • the process whereby organisms (not closely related) independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.
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9
Q

Homologous structures

A
  • evolution of homologous structures by adaptive radiation explains similarities in structure when there are differences in function
  • structures that look superficially different and perform a different function, but actually share structural similarity when looking closer at the bone positions
  • structure has the same origin/ancestor but they have become different because they perform different functions (adaptive radiation)
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10
Q

Analogous structures

A
  • structure is different, but function is similar
  • the structures have different origins, but have become similar over time because they perform the same/similar function (convergent evolution)
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11
Q

Speciation

A
  • the formation of new and distinct species in the course of evolution
  • requires barriers between gene pools to separate gene pools enough for the populations to be considered two separate species
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12
Q

Outline the barriers between gene pools

A
  • genetic isolation: gametes incompatible
  • temporal isolation: different breeding seasons
  • ecological isolation: usually in plants that are growing in different habitats; their gametes rarely cross paths
  • behavioural isolation: for example, bird dances only attract members of the same species
  • hybrid inviability: for example, mules (the product of a male donkey and a female horse) are infertile
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13
Q

Allopatric speciation

A

when one population is separated into two distinct populations by some geographical barrier (ie. river, elevation of mountain range, desert)

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14
Q

Sympatric speciation

A

individuals within a population acquire different traits while in the same geographic area (some other form of isolation occuring)

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15
Q

Explain the development of melanic insects in polluted areas with reference to evolution.

A
  • adult Biston betularia moths fly at night to try to find a mate and reproduce
  • during the day, they roost on the branches of trees - predators (ie. birds) predate moths during the day if they can find them
  • in unpolluted areas, tree branches are covered in pale-coloured lichens and peppered moths are well-camouflaged against them
  • however, in polluted areas, sulphur dioxide in the air kills lichens and the soot from coal burning blackens the tree branches
  • thus, melanic moths are well-camouflaged against the dark tree branches in polluted areas
  • therefore, in unpolluted areas, peppered moths are favoured and in polluted areas, melanic moths are favoured
  • natural selection does its job and the favoured species survives/reproduces
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16
Q

Continuous variation & gradual divergence

A
  • continuous variation is variation in which is quantitative and can have a range of values (ie. height)
  • matches the concept of gradual divergence, the idea that populations gradually diverge over time to become separate species
  • if gradual divergence is true, we would expect to be able to find examples of all stages of divergence
  • examples can be seen with Galapagos finches
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17
Q

Compare the pentadactyl limbs of different animals

A
  • the four vertebrate classes that have limbs, amphibians, reptiles, birds and mammals, all have pentadactyl limbs
  • crocodiles (reptiles) walk/crawl on land using their webbed hind limbs for swimming
  • penguins (birds) use their hind limbs for walking and their forelimbs as flippers for swimming
  • echidnas (mammals) use all four limbs for walking and also use their forelimbs for digging
  • frogs (amphibians) use all four limbs for walking and their hind limbs for jumping
  • although they have have pentadactyl limbs, they have different functions
  • differences can be seen in the relative lengths and thicknesses of the bones
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18
Q

Define natural selection

A

a process that leads to the increased reproduction of individuals with favourable heritable variations, as better adapted individuals tend to survive and reproduce more than the less well adapted individuals

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19
Q

Outline the process of natural selection

A
  • can only occur if there is variation amongst members of the same species
  • there is a struggle for survival
  • causes organisms that have favourable genetics (are better adapted) to survive while organisms that have unfavourable genetics (less well adapted) die/produce fewer offspring
  • individuals that reproduce pass on characteristics to their offspring
  • therefore, increases the frequency of characteristics that make an individual better adapted while decreasing the frequency of other characteristics (which do not make the individual better adapted); leads to changes within the species
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20
Q

What causes genetic variation?

A
  • mutations
  • meiosis
  • sexual reproduction
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21
Q

Define adaptation

A
  • characteristics that make an individual suited to its environment and way of life
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22
Q

Changes in beaks of finches on Daphne Major

A
  • there are 14 species of finches on Galapagos Islands, each having varying sizes and shapes of beaks
  • beak characteristics and diet are closely related; when one changes, the other does too
  • two finches of interest on the island Daphne Major: Geospiza fortis and Geospiza fuliginosa
  • G. fortis is a medium ground finch that can feed on small AND larger seeds, whilst G. fuliginosa can only feed on small seeds
  • resultantly, G. fuliginosa is nearly extinct
  • in 1977, a drought on Daphne Major caused a shortage of small seeds; G. fortis fed on the larger, harder seeds
  • most of the population died, with the highest mortality among the shorter beaks b/c larger beak makes it easier to crack open the larger seeds
  • in 1982-83, a severe El Nino event caused an increased supply of small, soft seeds and fewer large, hard seeds for 8 months
  • during the 8 months, G. fortis bred rapidly in response to the increase in food
  • after the 8 months, dry weather conditions ensued and breeding stopped until 1987
  • in 1987, G. fortis had longer and narrower beaks than the 1983 average, correlating with the reduction in supply of small seeds in 1977
  • variation in the shape and size of the beaks is mostly due to genes (heritability)
  • one of the objections to the theory of evolution by natural selection is that significant changes caused by natural selection have not been observed actually occuring; the case of G. fortis serves as an example of significant changes occurring as a result of natural selection
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23
Q

Explain the evolution of antibiotic resistance in bacteria

A
  • antibiotic resistance is due to genes in bacteria, so it can be inherited
  • begin with a population of bacteria without antibiotic resistance
  • bacteria receives antibiotic resistance gene either through mutation or from another bacterium from another population
  • when an antibiotic is used, the bacteria with resistance survive while the bacteria without the resistance die off (strong natural selection for resistance)
  • therefore, the bacteria with resistance reproduce and the population contains more antibiotic resistant bacteria
  • note: without the presence of antibiotic resistance, there is a weak natural selection against the gene for resistance; therefore, if you do not use antibiotics, the population will contain fewer bacteria with antibiotic resistance
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24
Q

Explain why the evolution of antibiotic resistance in bacteria is so rapid

A
  1. Widespread use of antibiotics (ie. treating diseases, animal feeds)
  2. Bacteria can reproduce rapidly (generation time of less than an hour)
  3. Populations of bacteria are often huge (increased chance of mutation)
  4. Bacteria can pass genes to other bacteria in several ways (ie. plasmids allow one species of bacteria to gain antibiotic resistance from another species)
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25
Q

What is an acquired characteristic?

A
  • characteristics that develop during the lifetime of an individual
  • STUDENTS SHOULD BE CLEAR THAT ACQUIRED CHARACTERISTICS ARE NOT HERITABLE
  • I repeat, the IB says that characteristics ACQUIRED DURING THE LIFETIME OF AN INDIVIDUAL are NOT HERITABLE
  • This is explicitly stated in the guidance, so regardless if it is 100% true or not, commit it to memory, okay?
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26
Q

State and explain the system used to name species, making reference to writing conventions

A
  • binomial system/binomial nomenclature
  • it is universal among biologists and has been agreed and developed at a series of congresses
  • the international name of a species consists of two words; the first is the genus and the second is the species
  • genus name begins with upper-case letter and the species name begins with lower-case letter
  • binomial is italicized (if typed) or underlined (if handwritten)
  • 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
  • the earliest published name for a species, from 1753 onwards for plants and 1758 onwards for animals, is the correct one
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27
Q

Explain what is meant by “hierarchy of taxa”

A
  • taxonomists classify species using a hierarchy of taxa
  • taxon is greek for “group of something” (taxa is the plural)
  • species are grouped into a genus; genera are grouped into families; families are grouped into orders and so on
  • the taxa form a hierarchy, as each taxon includes taxa from the level below
  • going up the hierarchy, the taxa include larger and larger numbers of species, which share fewer and fewer features
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28
Q

List the three domains

A

All organisms are classified into one the three following domains:

  1. eubacteria
  2. archaea
  3. eukaryota

Guidance: Viruses are not classified into any of the domains because they are NOT LIVING ORGANISMS

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29
Q

Eubacteria

A
  • organisms referred to as bacteria
  • no histones associated with DNA
  • introns are rare or absent
  • cell walls are made of chemical called peptidoglycan
  • cell membrane: glycerol-ester lipids; unbranched side chains; d-form of glycerol
30
Q

Archaea

A
  • organisms referred to as archaeans
  • found in a broad range of habitats (ie. ocean surface, deep ocean sediments, oil deposits below the surface of the Earth, extreme habitats like close-to-boiling or very salty water)
  • proteins similar to histones bound to DNA
  • introns present in some genes
  • cell walls are not made of peptidoglycan
  • cell membrane: glycerol-ester lipids; unbranched side chains; L-form of glycerol
31
Q

Eukaryota

A
  • organisms referred to as eukaryotes
  • histones associated with DNA are present
  • introns are frequently present
  • cell walls are not made of peptidoglycan; cell walls are not present in all eukaryotes
  • cell membrane: glycerol-ester lipids; unbranched side chains; d-form of glycerol
32
Q

List the principal taxa for classifying eukaryotes

A

Kingdom > Phylum > Class > Order > Family > Genus > Species

33
Q

List the kingdoms of eukaryote

A
  1. plants
  2. animals
  3. fungi
  4. protoctista
34
Q

Classify one animal species from domain to species level. (ie. Humans)

A

Answers may vary. (Example for humans:)

Domain: Eukaryota

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Primates

Family: Hominidae

Genus: Homo

Species: sapien

35
Q

Classify one plant species from domain to species level. (ie. Date palm)

A

Answers may vary. (Example for date palm:)

Domain: Eukaryota

Kingdom: Plantae

Phylum: Angiospermophyta

Class: Monocotyledoneae

Order: Palmales

Family: Arecaceae

Genus: Phoenix

Species: dactylifera

36
Q

Explain what is meant by “natural classification”

A
  • scientific consensus is to classify species in a way that most closely follows the way in which species evolved
  • all members of a genus or higher taxon should have a common ancestor
  • because of the common ancestry, we can expect the members of a natural group to share many characteristics
  • can be problematic because it is not always clear which groups of species share a common ancestor
  • convergent evolution can make distantly related organisms appear superficially similar
  • adaptive radiation can make closely related organisms appear different
37
Q

Explain what is meant by “unnatural/artificial classification”

A
  • an example of unnatural/artificial classification would be one in which birds, bats, and insects are grouped together on the basis that they all fly
  • flight evolved separately in these groups and as they do not share a common ancestor, they differ in many ways
  • plants and fungi were once grouped together (probably because they do not move and have cell walls), but this is an artificial classification as their cell walls evolved separately and molecular research shows that they are no more similar to each other than to animals
38
Q

List the advantages of natural classification

A
  • helps in the identification of species
  • allows the prediction of characteristics shared by species within a group
39
Q

Dichotomous keys

A
  • used in identifying specimens
  • a dichotomous key consists of a numbered series of pairs of descriptions; one description should clearly match the species and the other should be clearly wrong
  • each of the pair of descriptions either leads to another of the numbered pairs of descriptions in the key, or to an identification
  • a second type of dichotomous key is a branching flow chart
  • you should know how to construct a dichotomous key
40
Q

List the four phyla of the kingdom Plantae that IB wants us to know

A
  1. bryophyta
  2. filicinophyta
  3. coniferophyta
  4. angiospermophyta
41
Q

Bryophyta

A
  • 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
42
Q

Filicinophyta

A
  • 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
43
Q

Coniferophyta

A
  • has vascularisation (i.e xylem and phloem)
  • 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
44
Q

Angiospermophyta

A
  • has vascularisation (i.e xylem and phloem)
  • 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
45
Q

List the seven phyla of the kingdom Animalia that IB wants us to know

A
  1. porifera
  2. cnidaria
  3. platyhelminthes
  4. annelida
  5. mollusca
  6. arthropoda
  7. chordata
46
Q

Porifera

A
  • 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
47
Q

Cnidaria

A
  • 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
48
Q

Platyhelminthes

A
  • 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
49
Q

Annelida

A
  • have bilateral symmetry
  • have a separate mouth and anus
  • body composed of ringed segments with specialisation of segments
  • examples include earthworms and leeches
50
Q

Mollusca

A
  • have bilateral 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)
51
Q

Arthropoda

A
  • 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
52
Q

Chordata

A
  • 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)
53
Q

Define vertebrate

A
  • an organism that has a backbone composed of vertebrae
  • all of the organisms in the five largest classes of chordate are vertebrates
54
Q

List the five largest classes of chordate

A
  1. birds 2. mammals 3. amphibians 4. reptiles 5. fish
55
Q

Birds

A
  • 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)
56
Q

Mammals

A
  • 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)
57
Q

Amphibians

A
  • 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)
58
Q

Reptiles

A
  • 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)
59
Q

Fish

A
  • 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)
60
Q

Clade

A
  • a group of organisms that have evolved from a common ancestor
  • includes all species alive today, together with the common ancestral species and any species that evolved from it and then became extinct
61
Q

Evidence for which species are part of a clade

A
  • can be obtained from base sequences of genes or amino acid sequences of proteins
  • species that have a recent common ancestor can be expected to have few differences in base/amino acid sequences
  • species that diverged from a common ancestor tens of millions of years ago are likely to have many differences
62
Q

Molecular clock

A
  • sequence differences accumulate gradually, so there is a positive correlation between the number of difference between two species and the time since they diverged from a common ancestor
  • differences in the base sequence of DNA (and therefore, in the amino acid sequence) are the result of mutations
  • there is evidence that mutations occur at a roughly constant rate, so they can be used as a molecular clock
63
Q

Homologous trait

A
  • trait is similar because of similar ancestry
64
Q

Analogous trait

A
  • trait that is similar because of convergent evolution; they evolved independently
65
Q

Morphology

A
  • form and structure of organisms
  • rarely used for identifying members of a clade because of problems in distinguishing between homologous and analogous traits
66
Q

Cladogram

A
  • tree diagrams that show the most probable sequence of divergence in clades
  • almost always based on base or amino acid sequences
  • the branching points on cladograms are called nodes
  • usually two clades branch off at a node but sometimes there are three or more
  • the node represents a hypothetical ancestral species that split to form two or more species
67
Q

Construct a cladogram including humans and other primates

A
68
Q

Analysis of cladograms to deduce evolutionary relationships

A
  • the pattern of branching in a cladogram is assumed to match the evolutionary origins of each species
  • the sequence of splits at nodes is therefore a hypothetical sequence in which ancestors of existing clades diverged
  • if two clades are linked at a node, they are relatively closely related
  • some cladograms include numbers to indicate the number of differences in base/amino acid sequences or in genes
  • cladograms can provide strong evidence but cannot be regarded as proof for the evolutionary history of a group
69
Q

Reclassification of species

A
  • taxonomists sometimes reclassify groups of species when new evidence shows that a previous taxon contains species that have evolved from different ancestral species
  • evidence from cladistics has shown that classifications of some groups based on structure did not correspond with the evolutionary origins of a group of species
  • the usage of base/amino acid sequences to construct cladograms and identify clades has caused some revolutions in plant and animal classification
  • groups may be split up into two or more taxa
  • species classified in different taxa may be merged into one taxa
  • species may be moved from one genus to another or between higher taxa
70
Q

Reclassification of the figwort family

A
  • until recently, figworts were the 8th largest family of flowering plants, containing 275 genera
  • they were originally grouped together based on similarities in morphology
  • however, many of the figwort plants were too dissimilar in structure to function as a meaningful group
  • taxonomists investigated the evolutionary origins of the figwort family using cladistics, comparing the base sequences of three chloroplast genes in figworts
  • they found that the figwort family was not a true clade and that five clades had been incorrectly combined into one family
  • a major reclassification has now been carried out, with less than half of the species remaining in the figwort family (it is now the 36th largest family among angiosperms)