Chpts 15 & 16 Flashcards Preview

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Flashcards in Chpts 15 & 16 Deck (53):

What varies in each species DNA

Due to new genes gained by mutations and evolutionary mechanisms such as natural selection and genetic drift, the sequence of bases and the code in the DNA is different in different species


Explain how DNA differs in related species

Species distantly related have more differences in the DNA, species closer related share greater portion of their DNA

Examination of genome shows humans and chimps share more than 98% the same DNA


List the comparative studies in biochemistry DNA for evolution evidence

Junk DNA
endogenous retroviruses
Protein sequences
Ubiquitous proteins
comparative genomics


Explain junk DNA

Chromosomes that contain some non-coding sequences in bases of DNA, they have no function or purpose

More closely related species have more junk sequences in common, hence shows related species evolved from common ancestor


What are endogenous retroviruses

A viral sequence that because part of an organisms genome

Retroviruses become endogenous if it is inserted into a cell whose combinations will be inherited by the next generation- an ovum or a sperm cell


How do endogenous retro viruses (ERV) explain evolution

Offspring affected has same copy of ERV in same place, in same chromosome, in every cell
Other primates possess some of the same ERV's in exact same locations in their genomes


Describe mtDNA structure

Small circular molecules in mitochondria
37 genes (5 to 10 in each mitochondrion)
24 contain code to make RNA (needed for protein synthesis)
Other 13 instructions for making enzymes needed for cellular respiration reactions
Can only be inherited through mother


Explain mutations in mtDNA

mtDNA has higher mutation rate than nuclear DNA hence human mtDNA been slowly diverging from mtDNA of original female ancestor
mutation amount roughly proportional to amount of time that has passed


Explain mtDNA as evolution evidence

Can determine closeness of relationships- identical=closely related (maybe siblings), very different= maternal ancestor lived long ago

Allows scientists to trace migration routes and verify evidence from other sources


Explain protein sequences as evidence for evolution

Comparing the type and sequence of amino acids in similar proteins from different species to see similarities

Degree of difference estimate amount of evolution that has taken place since two species developed from a common ancestor


Explain ubiquitous proteins

One of a group of proteins that appears to be in all species from bacteria to humans
The small protein called ubiquitin is present in all cell types as they perform basic yet essential life functions - carry out same function no matter where they are


Ubiquitous proteins as evidence for evolution

Structure changed very little over millions of years, same structure appears in all sequences molecules --> descended from ancestral protein


Explain bioinformatics

Use of computers to describe molecular components of living things
Measures changes in DNA

Uses process called annotation to identify sequences (possible as genes have start and end codon) --> computers as genomes to long to annotate by hand


Explain comparative genomics

Genome sequences of different species compared to see similarities and differences

Identify evolutionary changes, identifying preserved genes and genes that give unique characteristics among species, reveals diversity of gene composition in different evolutionary lineages

Subtle differences between animal species are able to be teased apart

Revealed high similarity between chimps and humans


What is comparative anatomy

Involves structural features of related animals to ascertain degree of similarity between them

Similarities in structure suggest species have a common ancestor


List the three areas of comparative anatomy

Homologous organs
Vestigial organs


Explain embryology

Compare very early stages of embryonic development of organisms (in vertebrates)

All early embryos have two-chambered heart, a well developed tail, similar brain development and don't have paired appendages
Suggests evidence for common ancestor


Explain homologous structures

Using forelimbs of vertebrates

Bones arranged in similar ways however developed different functions, hence coming from common ancestor

Anthropoids show many anatomical resemblances with humans including similar structure of leg muscles in gorillas and humans = closely related= common ancestor


Explain vestigial organs

Structures of reduced size that appear to have no function (common in vertebrae species)
Humans may have as many of 90 of these structures including nicititating membrane, muscles that move ears, nipples, pyramidalis muscles, humans also have vertebrae for tail fused from coccyx and an appendix
Over time and with changing environments, organs no longer essential to survival and gradually reduced to vestigial organs
Not harmful so not eliminated - natural selection reduced organs as it would be a waste of organisms energy and resources to maintain useless structures
Will one day most likely disappear


Explain nicititating membrane

Third eyelid
Found in cats, frogs, birds, other vertebrates
Only seen in humans as pinkish membrane located in inner corner of eye


Explain muscles that move ears

Reduced to such an extent that most people's ears don't move at all, whereas still move for mammals


Explain nipples

No function on males however remain as human foetuses develop from same basic genetic form


Explain pyramidalis muscles

One fifth of population don't develop muscles that lie above pubic bone

Make no difference to muscular performance


Explain how geographical distribution of species can provide evidence for evolution

Same animal, many different species across world and within countries as species develop to suit their environment

Shows different species must have come from a common ancestor


List 7 best conditions for fossilisation

•Quick burial- buried by sand and mud deposited by rivers, volcanic ash, or other members of the species
•No oxygen- allows for complete preservation
•Presence of hard body parts
•absence of organisms that cause decay (dead organisms are usually decayed by microorganisms, however, if buried rapidly conditions not suitable for microorganism so decomposition slowed or prevented)
•most form near watery environment when buried in silt or mud
•ideal conditions: flood, volcanic eruption, earthquake (mineral rich conditions)


Common places fossils are found

Edges of lakes and rivers, in caves, volcanically active areas


How is a fossil formed

Organism walks across wet mud or volcanic ash forming footprints/something buried
Mud dries, ash remains undamaged
Fossil quickly covered and undisturbed
More layers of sediment fall on top to keep fossil preserved


Why can't animals be preserved in volcanic eruptions

Heat from volcanic material can destroy organism, however, fallen ash can preserve


List the unsuitable conditions for fossilisation

Wet, acidic soil- will dissolve minerals in the bones
Alkaline soils best suited for fossilisation


Why is soft tissue rarely fossilised

Fossilised soft tissue (e.g. muscle) is rarely found as it degrades quickly or is consumed by scavengers or bacteria


Define absolute dating

The actual date of the specimen in years - not always effective


Define relative dating

Tells us whether one sample is older or younger than another
Estimation of age placed on timeline


List the three methods of absolute dating

Potassium argon technique
Radio carbon technique
Tree ring dating (dendrochronology)


Explain potassium argon technique

Potassium-40 decays into argon-40 and calcium-40
By measuring amounts of these in organisms, the age of the fossil is able to be determined
Often used on rocks that surround fossil


Why use potassium argon technique

•fossil aged between 100000-200000 years old
•buried in volcanic eruption--> sometimes bad as means bone is buried deep


Explain radiocarbon dating

Based on radioactive decay of carbon-14 to nitrogen
By measuring amount of radiation liberated by a sample, the ratio of carbon-14 to carbon-12 can be estimated
From this age of sample can be calculated
Half life of carbon-14 is 5730(+-) 40 years-- takes 5730 years for half of the original amount of carbon to decay or disappear


How do human have carbon

Through photosynthesis carbon is created in plants. Humans and animals eat these plants hence consume carbon-14


Why use radiocarbon dating

•Accelerator mass spectrometry (AMS) has allowed for samples as small as 100mg to be tested
•Fossils aged up to 60000 years old
•Can be used to date artefacts (contain charcoal left from cooking)


Limitations of radiocarbon dating

Materials have to be organic
Technique has to be treated with caution- once assumed ratio of carbon-12 to carbon-14 in atmosphere was constant but it actually varies


Explain tree ring dating

Concentric rings are used to measure the age of the tree trunks that are found near human ancestral remains

Each ring represents one year of growth

Rings differ in width according to how favourable the growing season was

Certain rings produced in years of exceptional weather conditions can be used as marker rings

Starting with living trees it is possible to correlate marker rings with timber taken from ancient human structures


Advantages of tree ring dating

Useful in conjunction with radio-carbon dating to date human ancestral remains and artefacts up to 9000 years old


Limitations of tree ring dating

Particular conditions are needed for this method as timber is rarely preserved for more than a few thousand years


List the two methods of relative dating

Fluorine dating


Explain stratigraphy

The study of layers of strata
Can be done in two ways:
Principle of superposition
Correlation of rock strata


Explain principle of superposition

Layers of sedimentary rocks on top are younger than those beneath them, hence fossils inside layers
Has to be treated with caution
- distortion of earths crust (earthquakes) can cause rock layers to be turned upside down
- fossils and artefacts can be buried by early humans or animals hence actually younger than sediment layers above them


Explain correlation of rock strata

Matching rock layers from different areas by examining rock and studying fossils it contains
Rocks with same fossils are assumed to be the same age
Useful with index fossils


What are index fossils

Widely disturbed fossils, found in many different areas, only for a short period of time
Their age is known hence can confirm relative dates and ages of other fossils


What are phylogenetic relationships based on assumption that

Nucleotides sequences do not change over time


Explain the fossil record

Establishes evolutionary links between species/ shows common ancestry
Provides evidence of which organisms lived on earth in the past and which organisms are now extinct
Examples of transitional organisms between species


Why can stratigraphy not be used to accurately measure time

Sediments accumulate at different rates in different sedimentary environments

Rock record doesn't tell us how many years have passed between periods of rock deposition

Stratigraphy alone cannot be used to determine relative ages


Why are fossils hard to find

Could've been destroyed by earth movement, weather, or humans

People don't always realise what they find is a fossil

Archaelogists may be looking in the wrong place

Buried too deep or in inaccessible place


How to find most erosion in a layer

Look for common site in each layer
One closest to top = most erosion


List the problems with the fossil record

Incomplete fossils found

Not all organisms had representatives on the fossil record

Not all conditions produce fossils

Not all fossils have been discovered