topic 5 Flashcards
what is evolution
a change in allele frequency over generations
what is natural selection
when more advantageous alleles are more likely to passed onto offspring via reproduction leading to a gradual change in a species over time
evolution by gene mutation
- mutations introduce new alleles into a population.
- lead to advantageous traits
- these traits more likely to be passed on, leading to evolutionary change.
- increase genetic variation within a population.
evolution by natural selection
Variation + Selection Pressure → Advantageous Traits Survive → Traits Passed On → Population Adapts.
Evolution occurs when heritable traits change in frequency over generations due to these processes.
what is speciation
the development of a new species
what must happen in order for speciation to occur
there must be some sort of isolating mechanism that prevents successful interbreeding between populations of species
why is reproductive isolation important to speciation
when it happens there is no more exchange of genes.
it prevents gene floww
what are the two types of speciation
allopatric speciation
sympatric speciation
allopatric speciation
when populations are geographically isolated from one another
sympatric speciation
random mutations beween two populations cause them to become reproductively isolated in the same environment
with no geographical barrier
allopatric speciation
two species will be geographically isolated
will respond to different selection pressures
will become less like each other
random mutations will accumulate
allele frequencies will change
random changes in allele frequency will cause genetic drift if popoulation is small
once two populations meet and are unable to breed they will belong to two different species
sympatric speciation
two populations overlap with no geographical barrier, will not interbreed and produce fertile offspring, no gene flow there is reproductive isolation
how does reproductive isolation occur in sympatric speciation
when random changes in the alleles and therefore the phenotypes of some individuals in a population prevent them from successfully breeding with other individuals in the populationh
temporal isolation
species exist in same area but reproduce at different times
ecological isolation
species may occupy different parts of the habitat
behavioral isolation
do not respond to each others courting behaviour will not attract individuals of oppposite sex
physical incompatibility
physical barriers such as changes in genitalia with prevents successful mating
how will the changes lead to isolation
lack of gene flow between two populations means allele frequencies may change in diff ways
lead to changes in phenotypes of two populations
if enough allele frequency differences arise they will eventually no longer be able to breed with each other
how was evidence validated to support the theory of evolution
theory sent to a scientific journal and 2-3 scientists would peer review and examine critically to check if his work is valid (use proper controls, use statistics, justified conclusions) theory paper sent back to mendel for alterations or clarification
then published in journal
would be presented at a scientific conference
What is genomics?
The branch of science that determines the sequence of bases in DNA to study genes.
How does genomics provide evidence for evolution?
By comparing base sequences of equivalent genes across species, showing similarities that indicate common ancestry.
What does the level of similarity in base sequences indicate?
High similarity = Recent divergence from a common ancestor.
Low similarity = Divergence occurred a long time ago.
How can genomics help establish relationships between organisms?
By determining when species diverged, helping trace evolutionary relationships.
What is proteomics?
The study of proteins, specifically sequencing their amino acid order in the primary structure.
How does proteomics support evolution?
Similar amino acid sequences in proteins across species indicate common ancestry.
What does the similarity in amino acid sequences of proteins suggest?
High similarity = Recent divergence from a common ancestor.
Low similarity = Divergence occurred further back in time.
Why are proteins a reliable source of evidence for evolution?
The amino acid sequence is determined by DNA, linking proteomics to genomic evidence.
How are scientific journals important for validating evolutionary evidence?
They allow researchers to publish findings, which undergo peer review to ensure accuracy and credibility.
What role does peer review play in validating evidence for evolution?
Experts critically evaluate the evidence and methodology before it is accepted and published.
How do scientific conferences contribute to validating evidence for evolution?
They provide a platform for scientists to discuss, critique, and share new findings
How are genomics and proteomics used to measure evolutionary relationships?
By comparing DNA base sequences and protein amino acid sequences to establish when species diverged from a common ancestor.
Why is the similarity of genes and proteins across species significant?
It demonstrates shared ancestry and helps trace evolutionary history.
What are the four main types of evidence for climate change?
Records of atmospheric CO₂ levels (e.g., from ice cores).
Average global temperature records (from thermometer data).
Pollen grains preserved in peat bogs.
Dendrochronology (tree ring data).
What is the role of greenhouse gases in climate change?
Greenhouse gases, like CO₂, trap heat in the atmosphere, contributing to global warming.
How do scientists measure past atmospheric CO₂ levels?
By analysing gas bubbles trapped in ice cores.
How have CO₂ levels changed since the industrial revolution?
Pre-industrial levels peaked at ~300 ppm.
Current levels exceed 400 ppm, the highest in Earth’s history.
What does the correlation between CO₂ and temperature indicate?
Higher CO₂ levels are strongly linked to increased global temperatures, though correlation does not prove causation
How are average global temperatures measured?
By combining thermometer records from multiple locations worldwide over time.
What do temperature records since the mid-1800s show?
An overall trend of increasing global temperatures, despite short-term fluctuations.
What human activity corresponds with rising temperatures?
The burning of fossil fuels and subsequent release of CO₂.
How does peat form?
Under waterlogged and acidic conditions, partially decomposed plant matter compacts over time, forming peat layers.
How is pollen used to assess past climates?
Pollen grains in peat can identify plant species present at different times.
Plant species indicate climatic conditions (e.g., warm vs. cool climates).
What does an increase in warm-climate plant species in peat indicate?
A gradual warming of the climate.
What do tree rings represent?
One light ring and one dark ring together represent a full year of growth.
How does tree ring width indicate climate conditions?
Wider rings = Warmer, favorable growing conditions.
Narrower rings = Cooler, less favorable conditions.
What is a correlation?
A relationship where two variables change together, but one does not necessarily cause the other.
How is correlation between CO₂ and temperature validated as causal?
By understanding CO₂’s role as a greenhouse gas and eliminating other major influencing factors, scientists establish a strong causal link.
What is the greenhouse effect?
The process by which greenhouse gases absorb radiation re-emitted from the Earth’s surface, trapping heat in the atmosphere.
Why is the greenhouse effect essential for life on Earth?
It keeps Earth’s temperature stable enough to support life, preventing extreme fluctuations like those seen on Mars.
What are some examples of greenhouse gases?
Carbon dioxide (CO₂)
Methane (CH₄)
How have atmospheric CO₂ levels changed since the industrial revolution?
CO₂ levels have risen from ~280 ppm to over 400 ppm, the highest in Earth’s history.
What human activities contribute to increased CO₂ levels?
Burning fossil fuels for energy and transport.
Deforestation, soil degradation, and peat harvesting.
Ocean warming, reducing its ability to absorb CO₂.
What are carbon sinks?
Natural systems that store carbon, such as trees, soils, peat bogs, and oceans.
What is methane (CH₄)?
A simple hydrocarbon gas and the main component of natural gas, contributing to the greenhouse effect.
What human activities increase atmospheric methane levels?
Intensive farming of ruminant mammals (e.g., cattle).
Landfills decomposing organic waste.
Fossil fuel extraction.
How does global warming affect natural methane stores?
Warming permafrost releases stored methane, further enhancing global warming.
What is the observed correlation between CO₂ levels and global temperatures?
As CO₂ levels increase, global temperatures also rise, showing a strong correlation since the industrial revolution.
Can a causal relationship be concluded from CO₂ and temperature data alone?
No, but combined with knowledge of greenhouse gases, it provides strong evidence for human-driven warming.
What other factors influence global temperatures besides CO₂?
Natural events like solar winds, volcanic eruptions, and sunspots, though their impact is smaller.
How are past atmospheric CO₂ levels measured?
By analysing gas bubbles trapped in ice cores.
How do temperature records support anthropogenic climate change?
Thermometer data since the 1800s show an overall rise in global temperatures, correlating with increased CO₂ levels.
How can carbon emissions be reduced?
By limiting the burning of fossil fuels through alternatives such as biofuels and renewable energy sources.
What are biofuels?
Fuels made from recently living plant biomass, such as sugarcane.
Why are biofuels considered “carbon neutral”?
They release carbon that was recently absorbed by plants during photosynthesis, rather than carbon stored for millions of years like fossil fuels.
What are the advantages of using biofuels?
Often cheaper than oil.
Renewable and can be regrown quickly.
Considered carbon neutral.
What are the disadvantages of using biofuels?
Still release CO₂ when burned.
Require large amounts of land, reducing space for food production.
Habitat destruction (e.g., rainforests) harms biodiversity.
Cutting mature trees for biofuel growth reduces photosynthesis-based carbon removal.
Why does the production of biofuels involve CO₂ emissions?
Fossil fuels are used in cultivation, harvesting, processing, and transportation of biofuels.
How does land use change affect biofuel carbon neutrality?
Clearing land for biofuel crops releases stored carbon from vegetation and soil.
What is the impact of soil disturbance on carbon neutrality?
Soil disturbance during land preparation releases stored carbon into the atmosphere.
Why do indirect land use changes increase carbon emissions?
Growing biofuel crops displaces food crops, causing deforestation elsewhere to compensate.
