5.1 Evidence for evolution Flashcards
What does evolution describe?
Change over time
What encodes heritable characteristics?
Genes
What is the definition of biological evolution?
A change in the allele frequency of a populations gene pool over successive generations
How are heritable characteristics transferred between generations as?
Alleles
When talking about the evolutionary change in living organisms what is it referring to?
Heritable characteristics
How do fossil records provide evidence for evolution?
By revealing the features of an ancestor for comparison against living descendants
What is a fossil?
A fossil is the preserved remains or traces of any organism from the remote past
What do preserved remains provide?
They provide a direct evidence of ancestral forms
What do preserved remains include?
Bones
Teeth
Shells
Leaves etc
What do traces provide?
They provide indirect evidence of ancestral forms
What do traces include?
Footprints
Toothmarks
Burrows
Faeces
What is a fossil record?
The totality of fossils - both discovered and undiscovered
What does the fossil record show?
The fossil record shows that over time, changes have occurred in the features of living organisms
How can fossils be dated?
Fossils can be dated by determining the age of the rock layer in which the fossil is found
What is strata?
Rock layers
What does each strata represent?
Each strata represents a variable length of time that is classified according to a geological time scale
How do sedimentary rock layers develop and what does that mean?
Sedimentary rock develops in a chronological order meaning that the lower layers are older and the new strata form on top
What indicates a sequence of of development in the law of fossil succession?
That different kinds of organisms are found in rocks of particular ages in a consistent order
Describe where prokaryotes appear in the fossil record?
Prokaryotes appear in the fossil record before eukaryotes
Describe where fern appear in the fossil record?
Ferns appear in the fossil records before flowering plants
Describe where invertebrates appear in the fossil record?
Invertebrates appear in the fossil record before vertebrate species.
What is the law of fossil succession?
The chronological sequence of complexity by which characteristics appear to develop
What does the law of fossil succession suggest?
It suggests that newer species likely evolved as a result of changes to ancestral species.
Why do very few organisms become fossils?
Because fossilisation requires an unusual set of specific circumstances in order to occur
Why are only fragments of remains discovered?
As only the hard parts of an organism are typically preserved
What does the limited fossil data make it difficult to do?
It can make it difficult to discern the evolutionary patterns that result from ancestral forms
What do transitional fossils demonstrate?
Transitional fossils demonstrate the intermediary forms that occurred over the evolutionary pathway taken by a single genus
How do transitional fossils establish links between species?
By exhibiting traits common to both an ancestor and its predicted descendants
What is an archaeopteryx?
An example of a transitional fossil which links the evolution of dinosaurs (jaws, claws) to birds (feathers)
What is an australopithecus?
Australopithecus is an early hominin ancestor that first appears in the fossil record 4 million years ago.
What did larger cranial capacity evoke as an evolutionary advantage?
Increased intellectual prowess
What structural change caused changed dietary requirements (more meat)?
Smaller teeth and narrower jaw
What did a lower and broader pelvis evoke as an evolutionary advantage?
Altered birthing patterns for larger infants
What structural change reflected the used of fur clothing from hunting?
Marked reduction in body hair
What structural change was a consequence of improved diet?
Increased average height
What is selective breeding?
Selective breeding is a form of artificial selection where man intervenes in the breeding of species to produce desired traits in offspring
What does breeding members of a species with a desired trait result in?
The traits frequency becoming more common in successive generations
How does selective breeding provide evidence of evolution?
As targeted breeds can show significant variation in a short period
What has the selective breeding of plant crops resulted in?
The creation of new types of foods from the same ancestral plant source
What has been modified in the plants of the genus of brassica and what is the result?
Modified lower buds = broccoli
Modified leaf buds = Cabbage
Modified leaves = kale
What are three examples of animals that are used in selective breeding?
Horse, Cow and Dog
Why have race horses been bred and what does it result in them being?
Race horses have been bred for speed
Resulting in them being leaner, lighter, taller and quicker
Why have draft horses been bred and what does it result in them being?
Draft horses have been bred for power and endurance
Resulting in them being sturdier and stockier
Why have cows been selectively bred?
To produce offspring with improved milk production or increased muscle mass
What is a Belgian blue cow?
The type of cow that has been bred due to a mutation which have excessive bulk and produce more edible lean meat.
Why have hunting dogs been bred?
Hunting dogs have been bred to be smaller in stature so they could fit in fox holes
Why were herding dogs bred?
Herding dogs were bred for heightened intelligence in order to follow herding commands
Why were racing dogs bred?
Racing dogs were bred to be sleek and fast
Why were toy dogs bred?
Toy dogs were bred for their diminutive size
What are homologous structures?
Homologous structures are anatomical features that are similar in basic structure despite being used in different ways
The more similar the homologous structure between two species are, the…
The more closely related they are likely to be
What is adaptive radiation?
Where several new species diversify from an ancestral source with each new species adapted to utilise a specific unoccupied niche.
What does comparative anatomy show?
It may show certain structural features that are similar which shows common ancestry
What is a classic example of homologous structures?
The pentadactyl limb in a different variety of animals
How and why has the pentadactyl limb been adapted for humans?
Human hands are adapted for tool manipulation (power vs precision grip)
How and why has the pentadactyl limb been adapted for birds and bats?
Bird and bat wings have been adapted for flying
How and why has the pentadactyl limb been adapted for horses?
Horse hooves have been adapted for galloping
How and why has the pentadactyl limb been adapted for whales and dolphins?
Whale and dolphin fins have been adapted for swimming
What is genetic variation?
Variation which is inheritable
What will occur in any population of a given species?
Genetic variation
What is the type of variation that happens in genetic variation and why?
Continuous and will follow a normal distribution curve as the rate of change is gradual and cumulative
What does the degree of divergence depend on?
The extent of geographical separation and the amount of time since separation occurred
What will two populations of a species experience if they become geographically separated?
They will experience different ecological conditions
What will happen to the two populations of a species over time once they are geographically separated?
They will adapt to the different environmental conditions and gradually diverge from each other
What type of populations will experience less divergence?
Populations located in close proximity that separated recently
What type of population will experience more divergence?
Distant populations that separated a longer period of time ago
What is speciation?
The evolutionary process by which two related populations diverge into separate species
When are two populations considered to be separate species?
When they can no longer interbreed and produce fertile, viable offspring.
What happens to the degree of divergence the longer two graphically separated populations are separated?
It will gradually increase
What will happen as the genetic divergence between the population increases?
Their genetic compatibility decreases
What happens when two populations diverge to a certain extent?
They can no longer interbreed if returned to a shared environment
What are the two forms a peppered moth can exist as?
- a light colouration
- a darker melanic variant
What type of peppered moths are found in an unpolluted environment and why?
Lighter moths as the trees are covered in a pale-coloured lichen which the lighter moths can be camouflaged in
What type of peppered moths are found in a polluted environment and why?
Darker moths as the sulphur dioxide kills the lichen while soot blackens the bark which the darker moths can be camouflaged in
What moth was prominent before the industrial revolution and why?
The lighter moth as it has a survival advantage due to the environment being largely unpolluted
What moth was prominent after the industrial revolution and why?
The darker moth as it had a survival advantage due to environment being heavily polluted.
What are recent environmental policies in Europe doing in relation to the moths populations and why?
As they are reducing pollution levels, they are altering the frequency of the two moth populations
What is the frequency of the two different forms of peppered moth dependent on?
The environment thus it evolves as condition changes
What are the required conditions for fossilisation to occur and why?
- Hard body parts
- Preservation of remains
- High pressure to promote mineralisation of remains
- Anoxic conditions to protect against oxygen damage and prevent decomposition by saprotrophs
What are the stages of fossilisation?
- Death and decay
- Deposition
- Permineralization
- Erosion/ exposure
What happens during the death and decay stage of fossilisation?
Soft body parts are decomposed or scavenged this leaves the hard body parts
What happens during the deposition stage of fossilisation?
The hard remains are quickly covered with silt and sand and over time more layers continue to build
What happens during the permineralization stage of fossilisation?
Pressure from the covering layers of silt/sand causes the hard organic material to be replaced by minerals
What happens during the erosion/exposure stage of fossilisation?
Movement of earth plates may displace the fossil and return it to the surface for discovery
What is an epoch?
The smallest unit of time on the scale but it is still a period of millions of years
What are epochs grouped into?
Larger units called periods
What is an era?
An era is a subdivision combined of periods
What is an eon?
An eon is the largest division of geological time
What does the geological time scale measure?
Time on a scale involving four units
What is the division of time units in the scale based on?
The occurrence of a significant geological event like a mass extinction
What is comparative embryology and what does it show?
Studying the growing embryo in animals or plants shows that closely related species go through similar stages of development
What do the similarities in embryonic development suggest?
It suggests that the organisms shared a common evolutionary pathway
What do all terrestrial animals have as early embryos and what does it suggest?
Non functioning gill slits which suggests an aquatic origin
What do many vertebrates demonstrate at an early stage of embryonic development?
A primitive tail
What is a vestigial structure?
A functionless and reduced remnants of organs that were once present in their ancestors
What is an example of vestigial organ?
Pelvic bones in whales which suggests that whale ancestors were terrestrial mammals
What made vestigial organs vestigial organs?
Changes to the environment have rendered these organs redundant and so over time they have lost their functionality
What is biogeography?
Biogeography describes the distribution of lifeforms over geographical areas, both in past and present times
What can explain exceptions to the correlation between biogeographical distribution and common ancestory?
Continental drift
What are two pieces of evidence to suggest biogeographical distribution indicates shared ancestory?
- Most modern marsupials are found almost exclusively in Australia
- Australia has few placental mammals compared to south America even though environmental conditions are similar
Where are related species usually found?
In close physical proximity to each other
What do fossils found in the a particular region tend to resemble?
They closely resemble the modern organisms of the region
What are radioisotopes?
Radioisotopes are alternative forms of an element that have the same number of protons but a different number of neutrons
What does radioactive dating involve?
It involves comparing the ratio of radioactive isotopes in the fossil to that found in the atmosphere today
What are the three types of radioactive decay that can occur?
Alpha
Beta
Gamma
What is alpha decay?
Atom releases two protons and two neutrons to form a new more stable element
What is beta decay?
A neutron decays to produce a proton, electron and anti-neutrino
What is gamma decay?
Involves the release of electromagnetic radiation but does not change the mass of the atom
What stops alpha radiation?
Paper
What stops beta radiation?
Wood
What stops gamma radiation?
Lead
What is a half life?
Where radioisotopes decay at a constant rate and the time taken for half the original radioisotope to decay
What is Electron spin resonance a useful dating tool for?
Dating organic samples that are aged between 50,000 and 500,000 years old
What does ESR depend on?
The fact that when objects are buried they are bombarded by natural radiation from the soil
In ESR what is used to determine when the sample was buried?
The number of high energy electrons
In ESR what causes the electrons in minerals to move to and remain in a higher energy state?
Natural radiation from the soil
What does index fossils represent?
Short-lived species
Where can you only find index fossils?
In a restricted depth of rock strata
What can index fossils be used to do?
They can be used to synchronise the ages of rock layers when other dating techniques are not available
What does long range dating do?
Dates the rocks around the fossil to determine an age range
Where can dating be undertaken?
On igneous rock and not on the fossils themselves or the sedimentary rock they are found in
\what do all living things contain?
Carbon
What are the two isotopes of carbon found in someone?
C12 (stable) and C14 (radioactive)
When the living thing is alive what do the carbon isotopes do?
They will mirror environmental levels as carbon is constantly being cycled
What happens to the carbon when the living thing dies?
The ratio isn’t fixed as C14 breaks down in N14 through beta decay
What is the time frame of dating samples with carbon?
anything less than 60,000 years old
How do scientist use carbon to determine how long ago a creature died?
By measuring the amount of C14 remains in the sample
