B5 Flashcards
What is evolution?
Evolution is the gradual change in a species over time
How do organisms evolve?
Organisms evolve through natural selection because in a species there is normally a wide genetic variation. When further mutations happen, genetic variation increases
What is natural selection?
When mutations occur and those better adapted to the environment reproduce and those while the others die out and so evolving.
What is survival of the fittest?
When organisms better suited to their environment survive and those that aren’t, die out.
What is variation?
Differences within a species which give the organism its appearance (phenotype)
What is a mutation?
Changes in the gene sequence that arise spontaneously
How fast do bacteria reproduce?
Double every 20 minutes
What happens if there is a mutation in bacteria?
They usually aren’t favourable and the bacteria die instantly however sometimes mutations are favourable such as antibiotic resistance.
How do different species come about?
When there is so much generic variation and they can’t reproduce together anymore.
What are fossils?
They are formed when animals and plant remains are preserved in rocks.
How are fossils in different rock layers different?
The most recent layer is usually at the top
What is a fossil record?
When fossil layers form a sequence showing how an organism has gradually changed over time.
Where are the simplest organisms found (in terms of fossils)?
In the oldest rocks
Where are more complex organisms found (in terms of fossils)?
Organisms such as vertebrates are found in more recent rocks
How are fossils formed?
- The reptile dies and falls to the ground
- The flesh rots, leaving the skeleton covered in sand or soil before it’s damaged.
- The skeleton becomes mineralised and turns into rock after millions of years
- The fossil eventually emerges as rocks move and erosion takes place.
What do scientists look at for molecular comparisons between species?
The order of nucleic acid bases or the order of amino acids in a protein.
What is a creationist?
Someone who doesn’t believe in the theory of evolution.
What is an evolutionist?
Someone who believes in the theory of evolution
What type of ‘evolution’ did people believe from 384 BCE to the 1600s?
Spontaneous Generation
Who proposed the idea of spontaneous generation?
Aristotle
What is spontaneous generation?
The idea that life came from non-living material if the material contained vital heat (pneuma)
Who are the four men that significantly contributed to the theory of evolution?
Jean-Baptise Lamarck
Charles Lyell
Charles Darwin
Alfred Wallace
What is Lamarckism?
The idea that an organism could evolve just by thinking it in response to an environmental change
Who was Charles Lyell?
A Scottish geologist whose book, Principles of Geology, inspired Charles Darwin
What did Charles Lyell suggest?
That fossils were evidence of animals that had lived millions of years ago
That Geologic processes are due to natural events “not god”
Who was Charles Darwin
A man who believed that all organisms evolved though simple to more complex organisms
What were Darwins’s key ideas?
Inherited traits
Variation in population
Offspring competed for limited resources
Evolution by natural selection (survival of the fittest)
When did people believe in spontaneous generation?
384 BC to the 1600s
When was the time of Lamarckism?
1744-1829
When was the time of Charles Lyell?
1797 - 1875
When was the time of Charles Darwin?
1809 - 1882
Who was Alfred Wallace?
The man who independently proposed the theory of evolution by natural selection
When was the time of Alfred Wallace?
1809 - 1882
What were Alfred Wallace’s key ideas?
Living things change over long periods of time
Survival of the fittest
Advantageous characteristics passed onto offspring
Speciation by reproductive isolation (Wallace effect)
What did Alfred Wallace and Charles Darwin do together?
Publish a book called ‘on the origin of species’
What did Wallace and Darwin challenge with their ideas?
They challenged the common belief that God created all living beings
What is classification?
The process of sorting living organisms into groups in which organisms within each group share similar characteristics
Why do scientists classify organisms?
Identify species
Predict characteristics
Find/show evolution
What is the taxonomy system?
A system that divides organisms into 5 kingdoms
What are the kingdoms of the taxonomy system?
Plants
Animals
Fungi
Protoctista
Prokaryotes
What happens as you move down the hierarchy of the taxonomy system?
The organism share more and more characteristics
What does the taxonomy system end in?
It ends in organisms being classified as individual species
What is binomial nomenclature.
A system used to name living organisms in Latin.
What is the first part of an organism’s Latin name known as?
The genus (surname) - it is shared by close relatives
What is the second part of an organisms Latin name known as?
The species - no two species have the same name
What is artificial classification?
When you group organisms based on their observable characteristics - evolutionary relationships aren’t taken into account
Why is artificial classification bad?
It can lead to difficulties in accurate classification
What is natural classification?
When scientists group organisms based on common ancestors by using DNA sequencing
What is phylogeny?
The study of evolutionary links
How are phylogenic links established?
By studying the similarities and differences in DNA between species
What is variation?
Differences within a species (height, hair colour…)
What is the phenotype of an organism?
The appearance of an organism
What are the 2 causes of variation?
Genetic variation
Environmental variation
What is genetic variation?
Variation caused by an organism’s genetic material
What is environmental variation?
Variation due to the environment in which you live in
What is continuos variation?
Variation which can take any value between and minimum and a maximum (height)
Wha is discontinuous variation?
Characteristic which falls into distinct group (your blood type)
What can cause continuous variation?
Genetic and environmental variation
What can cause discontinuous variation?
Genetic variation
What are examples of continuous variation?
Surface area of a leaf
Length of fur
Skin colour
What are some examples of discontinuous variation?
Gender
Eye colour
Wrinkled or non-wrinkled seeds
What type of graph is used to display continuous variation?
Histograms (the bars are often removed for lines)
What type of graph is used to display discontinuous variation?
A bar chart
What is asexual reproduction?
Reproduction which only includes one parent and the resulting daughter cell becoming a clone of the parent
What process does asexual reproduction use?
Mitosis
What are some examples of plants that reproduce asexually?
Potato plants
Spider plants
Daffodils
What is sexual reproduction?
Reproduction that needs 2 parents with the offspring not being identical
What does sexual reproduction result in?
It results the offspring having a variation
What are the gametes?
The male and female sex cells
What is fertilisation?
A process in which the gametes fuse together
What are the advantages and disadvantages of asexual reproduction?
If the parent is well adapted, the offspring will get all the characteristics
Only one parents is needed so large numbers of offspring are produced quickly
Bad changes in biotic or abiotic factors might end the species as all organisms will be affected
What are advantages and disadvantages of sexual reproduction?
Variation in offspring leads to evolution in a species so that they can cope with their environment
Reproduction is slower as it requires two parents so fewer offspring are produced
What is a diploid cell?
A cell with two sets of each chromosomes (a diploid cell in humans has 46 chromosomes)
What is a haploid cell?
A cell with one of each chromosome (gametes have 23 chromosomes)
What happens during fertilisation?
Two haploid gametes cells join together to form a diploid zygote
How does a zygote divide and why?
It divides by mitosis to produce a new organism
What is a genome?
The entire genetic material of an organism
How are gametes produced?
Through meiosis - 4 haploid cells from one diploid cell
How does meiosis create genetic variation?
All the cells are genetically different from each other and the parent cell
What are alleles?
Different forms of a gene
What is a dominant allele?
An allele that will get shown even if it is just from 1 parent
What is a recessive allele?
An allele that will only be shown if you acquire it from both parents
How are dominant and recessive alleles represented?
In caps and lowercase respectively
How would a characteristic be homozygous dominant?
If there were two of the dominant allele
How would a characteristic be homozygous recessive?
If there were two recessive alleles
How would a characteristic be heterozygous?
If there were different versions of a gene (a dominant and recessive allele) - usually write the dominant allele first
What are some dominant characteristics?
Dark, wavy hair
Brown eyes
Free ear lobes
Ability to roll tongue
Straight nose
Projecting chin
Freckles
What are some examples of recessive characteristics?
Straight, blonde hair
Blue eyes
Joined earlobes
Receding chin
Upturned nose
Inability to roll tongue
No freckles
What happens when two homozygous organisms are crossed?
The dominant allele will be shown
How do you know if you are a female (according to chromosomes)?
If you have two large X chromosomes
How would you know if you are male (according to chromosomes)?
If you have one large X chromosome and a smaller Y chromosome
What parent determines the gender of the child and how?
The father as speed can have either an x or a Y chromosome but all female gametes have X chromosomes
What is a mutation?
When the sequence of DNA bases is altered
What is a genetic variant?
A different version of an allele that is caused by a change in DNA
What does the position of the mutation in a DNA sequence determine?
It determines the effect that it will have on the organism
How many chromosomes does a human have?
46
What do mutation cause?
Mostly, the mutation won’t affect an organism’s phenotype
Some mutations may influence an organism’s phenotype
A few mutations will determine an organism’s phenotype - these lead to the variation that can be seen within a species
How are most mutations harmful?
They can cause cancer
They cause the production of abnormal protein channels - cystic fibrosis
They cause different shaped protein molecules to be made x sickle cell anaemia
What happens during cancer?
Cells grow and divide uncontrollably
How are some mutations neutral?
Some don’t benefit or harm the organism such as the mutation of not being able to roll your tongue
How can some mutations be helpful?
Mutations in bacteria could allow they to be resistant to antibiotics, increasing the chance of survival
What is a strand of DNA organised into?
Sections of coding DNA (genes) separated by sections of non-coding DNA
What might happen if a mutation occurs within a gene?
DNA bases might get changed, added or deleted
What happens if DNA bases get changed, added or deleted?
The order of bases (in mRNA) reduced during transcription may be different
What happens if mRNA produced is different due to a mutation?
The amino acids might assemble in a different order
The wrong protein may be produced
It may fold incorrectly and form a different shape
What might happen if a mutation happened to an enzyme?
Its active site may change shape - can’t bind to its substrate and catalyse the specific reaction
What happens if a mutation happens in non-coding DNA?
The gene may not be transcribed into mRNA at all - the protein won’t be produced
