topic 5 Flashcards
when does evolution occur?
when heritable characteristics of a species change
what is the mechanism of evolution?
natural selection
fossil record
- many sequences of fossils are known, which link together existing organisms with their likely ancestors
- sequence in which fossils appear matches the sequence in which they would be expected to evolve, with bacteria/simple algae appearing first, then fungi and worms, and then land vertebrates
- sequence fits with the ecology of the groups, with plant fossils appearing before animal, plants on land before animals on land, and plants suitable for insect pollination before insect pollinators
selective breeding of domesticated animals
- by breeding members of a species with a desired trait, the frequency of this trait becomes more common in successive generations
- targeted breeds can show significant variation in a (relatively) short period
- this shows that selection can cause evolution
homologous structures
Comparative anatomy of groups of organisms may show certain structural features that are similar, implying common ancestry
the evolution of homologous structures by adaptive radiation explains similarities in structure when there are differences in function
define adaptive radiation
when several new species rapidly diversify from an ancestral source, with each new species adapted to utilise a specific unoccupied niche
define homologous structures
Anatomical features that are similar in basic structure despite being used in different ways
speciation
- speciation is the evolutionary process by which two related populations gradually diverge into separate species that can no longer interbreed and produce fertile offspring
- the degree of genetic divergence between geographically separated populations will gradually increase the longer they are separated
give 5 pieces of evidence for evolution
- fossil record
- selective breeding of domesticated animals
- homologous structures
- speciation
- patterns of variation
patterns of variation
- continuous variation across the geographical range of related populations matches the concept of gradual divergence
- Darwin gave examples of populations that are recognisably different, but not the the extent that they are clearly separate species
- this disproves the idea that species were created as distinct types (and should be constant across their geographic range) or that they are unchanging
give an example of a homologous structure and explain its significance
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
however, they may also be highly dissimilar according to the mode of locomotion:
eg Human hands are adapted for tool manipulation (power vs precision grip),
Bird and bat wings are adapted for flying, whale and dolphin fins are adapted for swimming
describe the development of melanistic insects in polluted areas
Peppered moths (Biston betularia) exist in two distinct forms – a light colouration and a darker melanic variant
- 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.
- birds and other animals that hunt in daylight predate moths if they find them.
- in unpolluted areas tree branches are covered in pale-coloured lichens and peppered moths are well camouflaged against them.
- sulphur dioxide pollution kills lichens. Soot from coal burning blackens tree branches.
- melanic moths are well camouflaged against dark tree branches in polluted areas.
- in polluted areas the melanic variety replaced the peppered variety over a relatively short time, but not in non-polluted areas
natural selection can only occur if
there is variation amongst members of the same species - if all individuals in a population were identical, there would be no way of some being favoured over others
give 3 sources of variation
- mutation - new alleles produced by gene mutations enlarge the gene pool of a population
- meiosis - produces new combinations of alleles by breaking up the existing combination in a diploid cell, through crossing over and the independent orientation of bivalents
- sexual reproduction involves the fusion of male and female gametes, ensuring a new combination of alleles.
define adaptations
characteristics that make an individual suited to its environment and way of life. these develop by natural selection over time.
species tend to
produce more offspring than the environment can support, which may lead to a struggle for existence within a population due to competition for resources
describe how natural selection leads to change within a species
- individuals that are better adapted tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring
- individuals that reproduce pass on genetic characteristics to their offspring
natural selection thus increases the frequency of characteristics that make individuals better adapted and decreases the frequency of other characteristics leading to changes within a species.
give an example of adaptive radiation and natural selection
changes in beaks of finches on Daphne major
Different finch species demonstrated adaptive radiation and show marked variation in beak size and shape according to diet.
G. fortis’ diet consists of seeds, which when weather conditions are normal are plentiful, small, and soft, but which become fewer, larger, and tougher during times of drought
The Grants observed a wide range of beak sizes in G. fortis when weather conditions were normal, but found that during periods of drought beak size increased
This is because G. fortis were forced to feed on larger, harder seeds, which only the larger-beaked individuals were able to crack open, so most of the population died.
give 4 reasons why antibiotic resistance has grown so quickly
- there has been very widespread use of antibiotics, both for treating diseases and in animal feeds used on farms.
- bacteria reproduce very rapidly, with a generation time of less than an hour.
- populations of bacteria are often huge, increasing the chance of a gene for antibiotic resistance being formed by mutation.
- bacteria can pass genes on to other bacteria in several ways, including using plasmids, which allow one species of bacteria to gain antibiotic resistance genes from another species.
describe the process of development of antibiotic resistance
- there is a population with no antibiotic-resistant bacteria
- an antibiotic resistance gene is formed by mutation in one bacterium//received from a bacterium in another population
- population with some antibiotic-resistant bacteria
- when the antibiotic is used natural selection takes place
what is the binomial system?
a system of scientific names for species that is universal among biologists and has been agreed and developed at a series of congresses. this is applied whenever species are discovered
give 4 rules of the binomial system
- the genus name begins with an upper-case (capital) letter and the species name with a lower-case (small) letter.
- 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
- the earliest published name for a species is the correct one
how do taxonomists classify species?
using a hierarchy of taxa
state the 3 domains into which all organisms are classified
bacteria, archaea, eukaryota
bacteria
- histones associated with DNA
- presence of introns
- structure of cell walls
- cell membrane
- absent
- rare or absent
- made of peptidoglycan
- glycerol-ester lipids; unbranched side chains; d-form of glycerol
archaea
- histones associated with DNA
- presence of introns
- structure of cell walls
- cell membrane
- proteins similar to histones bound to DNA
- present in some genes
- not made of peptidoglycan
- glycerol-ether lipids; unbranched side chains; l-form of glycerol
eukaryota
- histones associated with DNA
- presence of introns
- structure of cell walls
- cell membrane
- present
- frequent
- not made of peptidoglycan; not always present
- glycerol-ester lipids; unbranched side chains; d-form of glycerol
state the 7 taxa used to classify eukaryotes
kingdom
phylum
class
order
family
genus
species
(katy Perry comes over for grape soda)
going up the taxa hierarchy, the taxa include ——– numbers of species which share —— features
larger; fewer
in natural classification, the genus and accompanying higher taxa consist of
all the species that have evolved from one common ancestral species
state and explain the two advantages of natural classification
- Identification of species is easier; if a new organism is found and it is not obvious what species it is, this can be identified by first assigning it to a kingdom, then the phylum, and so on.
- Because all of the members of a group in a natural classification have evolved from a common ancestral species, they inherit similar characteristics. This allows prediction of the characteristics of species within a group
describe the process of reviewing classification
taxonomists sometimes reclassify groups of species when new evidence shows that a previous taxon contains species that have evolved from different ancestral species
what are dichotomous keys used for?
used to identify different organisms, based the organism’s observable traits
state the 4 main plant phyla
- Bryophyta - mosses, liverworts, hornworts
- filicinophyta - ferns
- coniferophyta - conifers
- angiospermophyta - flowering plants
bryophyta
structures
vascularisation
reproduction
other features
filicinophyta
structures
vascularisation
reproduction
other features
coniferophyta
structures
vascularisation
reproduction
other features
angiospermophyta
structures
vascularisation
reproduction
other features
state the 7 main animal phyla
Porifera, cnidaria, Platyhelminthes, annelida, Mollusca and anthropda, chordata
learn the characteristics of each animal phyla
learn the features of each of the vertebrate classes
birds, mammals, amphibians, reptiles and fish (
classify the grey wolf
K- animalia
P- chordata
C- mammalia
O- carnivora
F- carnidae
G- canis
S- lupus
classify the date palm
K- plantae
P- angiospermophyta
C- monocotyledoneae
O- palmales
F- arecaceae
G- phoenix
S- dactylifera
define a clade
a group of organisms that have evolved from a common ancestor
how can we identify members of a clade?
from the base sequences of a gene or the corresponding amino acid sequence of a protein
describe the concept of molecular clocks
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
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
traits can either be
analogous or homologous
describe the difference between analogous and homologous traits
- homologous structures are similar because of similar ancestry (eg chicken wing/human arm/other pentadactyl forelimbs)
- analogous structures are similar because of convergent evolution (show similarities in structure but evolved independently)
why is morphology (form and structure) now rarely used for identifying members of a clade?
evidence from cladistics has shown that classifications of some groups based on structure did not correspond with the evolutionary origins of a group or species, leading to reclassification.
problems in distinguishing homologous and analogous structures have led to classification mistakes in the past, so evidence from base/amino acid sequences is trusted more
define cladograms
tree diagrams that show the most probable sequence of divergence in clades
branching in a cladogram is assumed to match
the hypothetical ancestral species splitting to form two or more species
describe cladograms including humans and other primates
check photo
give the key features of a cladogram
check photo
describe the issues with classification of the figwort family
- until recently the 8th largest family of angiosperms was Scrophulariaceae (aka figwort family), based on similarities in morphology
- taxonomists recently investigated the evolutionary origins of the figwort family using cladistics and base sequencing
- it was found that species in the figwort family were not a true clade and that 5 clades had incorrectly been combined into one.
Porifera
- symmetry
- body cavity
- segmentation
- other features
- examples
asymmetrical
none (have pores)
none
have spicules for support
sea sponge
cnidaria
- symmetry
- body cavity
- segmentation
- other features
- examples
radial
mouth but no anus
none
stinging cells (cnidocytes)
jellyfish, coral, sea anemone
Mollusca
- symmetry
- body cavity
- segmentation
- other features
- examples
bilateral
mouth and anus
non-visible (mantle and food)
may have a shell (made by mantle)
snail, octopus, squid, bivalves
platyhelmintha
- symmetry
- body cavity
- segmentation
- other features
- examples
bilateral
mouth but no anus
none
flattened body (increase sa:vol ratio)
tapeworm, planaria
annelida
- symmetry
- body cavity
- segmentation
- other features
- examples
bilateral
mouth and anus
segmented
move via peristalsis
earthworm, leech
anthropoda
- symmetry
- body cavity
- segmentation
- other features
- examples
bilateral
mouth and anus
segmented
exoskeleton (chitin)
insects, spiders, crustaceans
vertebrate classes
fish
amphibian
reptile
bird
mammal
fish
- body covering
- reproduction
- breathing
- temperature
- other features
scales made out of bony plates
external
gills
ectothermic
have a swim bladder
amphibian
- body covering
- reproduction
- breathing
- temperature
- other features
moist skin
external
simple lungs and via skin
ectothermic
larval state in water, adult state on land
reptile
- body covering
- reproduction
- breathing
- temperature
- other features
scales made out of keratin
internal (lays soft eggs)
lungs with extensive folding
ectothermic
simple teeth with no living tissue
bird
- body covering
- reproduction
- breathing
- temperature
- other features
feathers
internal (lays hard eggs_
lungs with bronchial tubes
endothermic
have wings and beaks with no teeth
mammals
- body covering
- reproduction
- breathing
- temperature
- other features
hair
internal - live births (except monotremes)
lungs with alveoli
endothermic
feed young with milk from mammary gland
