Bi0 5 Flashcards
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
mBank
• 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
D
-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,
color 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.q.
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 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)
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
5.4 Define a clade,
cladogram and cladistics
• 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.
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 Hominid 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
