3. Classification And Evolution Flashcards
Need for classification
- for convenience
- Makes it easy to identify organisms
- Makes it easier to study organisms
- Allows us to see the relationships between organisms
Classification top to bottom
Domain, kingdom, phylum, class, order , family, genus, species
Domain
(archaea, eubacteria, eukaryotae)
Kingdom
plantae, animalia, fungi, protoctista, prokaryotae)
Phylum
whether or not they have a backbone) chordata = animals w/ backbones
Class
general traits e.g. number of legs + arms)
Order
depends on what they eat)
Family
closely related group within order)
Species biological definition
a group of organisms that can interbreed to produce a fertile offspring =
Phylogenetic definition of species
a group of individual organisms that are very similar in appearance, anatomy, physiology, biochemistry and genetics
Features of protoctista
- eukaryotic
- Aquatic
- Most unicellular
- Autotrophic or heterotrophic
Plant responses to defend themselves from herbivores:
- chemicals (phenols)
- Folding
- Stings
Autotroph
make their own nutrients
Heterotroph
organisms that eats other plants or animals for energy and nutrients
Q
Binomial naming system
- first name is always the genus
- Second part of the name is the species
- The first letter in the genus is a capital letter and the species is in lower case (it all is in italics) = allows everyone to use the same naming system which simplifies research
Advantage of binomial naming system
universal and helps know which genus it belongs to
Prokaryotae
have no nucleus
have a loop of DNA that is not arranged in linear chromosomes
• have naked DNA (DNA that is not associated with histone proteins)
• have no membrane-bound organelles
• have smaller ribosomes than in other groups
• have cells smaller than those of eukaryotes
• may be tree-living or parasitic (some cause diseases)
Protoctista
• are eukaryotic
• are mostly single celled (but many algae are multicellular)
• show a wide variety of forms (the only thing that all protoctists have in common is that they do not qualify to belong to any of the other four kingdoms!)
• show various plant-like or animal-like features
• are mostly free-living
• have autotrophic or heterotrophic nutrition - some photosynthesise, some ingest prey.
some feed using extracellular enzymes (like fungi do), and some are parasites
Fungi
• are eukaryotic
• can exist as single cells (called yeasts) or they have a mycelium that consists of hyphae
• have walls made of chitin
• have cytoplasm that is multinucleate
•are mostly free-living and saprophytic - this means that they cause decay of organic matter
Plantae
• are eukaryotic are multicellular
have cells surrounded by a cellulose cell wall
• are autotrophic (absorb simple molecules and build them into larger organic molecules)
• contain chlorophyll
Animalia
• are eukaryotic are multicellular
• heterotrophic (digest large organic molecules to form smaller molecules for absorption)
• are usually able to move around
How is genetic material in bacteria held?
- dna loop free in cytoplasm
- Not associated w histone
Defining features of eukarya
- nucleus
- DNA w histone
- Membrane bound organelles
Evidence to classify organisms
DNA, biological evidence, conversion evolution
Conversion evolution
concept of organisms from different species could adapt in similar ways and therefore look similar
Biological evolution
look at molecules such as cytochrome C (protein found in mitochondria used for respiration) something that we all have because we all respire. You can compare the sequence of amino acids so the smaller the number of differences in the cytochrome c proteins, the more closer they are related
Why do we look at biological evidence
because conversion evolution is misleading
Looking at dna
some sequences highly conserved so comparison. Similar sequence indicates recent common ancestor. This is the best way to check but it can be time consuming. If there are differences it may be due to mutations which is a sign of evolution.
3 domain classification
- Bacteria, archaea, eukaryotic
- Bacteria, archaea, eukaryotic closeness
archaea and the bacteria are quite different, archaea are closer to the eukaryotic
Main difference between archaea and bacteria
cell membrane structure, presence and absence of flagella, use of different enzymes for protein synthesis, different methods of DNA replication and RNA synthesis
Similarities between archaea and eukaryotic
use similar enzymes for synthesis of RNA (rna polymerase), similar mechanisms of dna replication, both of them have proteins bound to their dna
Why did they come up w 3 domain system
due to a study of the RRNA sequence = more similar = more closely related and vice versa so they must’ve evolved separately a long time ago
Phylogeny
the study of the evolutionary relationship between organisms
2 types of classification
Artificial and natural
Artificial classification
look at features and put it into one group e.g. anything with wings = bird = for convenience.
Natural classification
look at genetic biodiversity to group organisms. Look at many characteristics = aim is to be able to reflect on evolutionary relationships and classify them
Conversion theory
two organisms can look the same because of adaptations to their environment, but not actually be part of the same species
Who found evidence for natural selection
Charles Darwin
Wallace
another scientist who came up with the same conclusion so they both joined together and discussed natural selection = similar ideas to Darwin which he arrived at independently + they published together
Darwin’s conclusions after his discovery
there is a struggle to survive, better adapted individuals survive and pass on their characteristic, a number of changes can give rise to a new specie
Darwin’s observations
offspring generally appear similar to their parents, no two individuals are identical, organisms have the ability to produce a large number of offspring’s, population in nature tends to remain fairly stable in size.
Why would an organism survive in an environment
need alleles for it so a mutation should occur, this gives rise to a new advantageous allele which is selected for, so organisms with that allele can reproduce and pass it on and over generations it can give rise to a new specie. = genetic variation within species, selection pressure in the environment and organisms that are better adapted survive and reproduce and pass on their genes
Evidence that shows evolution
fossils (can see features that have remained and changed in an organism), biological molecules (check which molecules have remained over many years = must have played a significant role in our lives = those who didn’t have that molecule, didn’t make it), compare dna sequences to check for any differences,
Fossils
deeper in ground are older than those near surface
Mutation in mDNA
- During reproduction, the mitochondria of the egg cells are passed on to the offspring = mDNA. This dna doesn’t go through all the checking that normal dna goes through, usually a lot of mutation in the mDNA that we can look for.
Variation
Difference between individuals
2 classifications
Continuous, discontinuous
Continuous
two extremes, but can’t be put into categories = range of values
Discontinuous
distinct categories
Intraspecific variation
When there’s variations within the same specie
Interspecific variation
When there’s variation between 2 diffferent species
2 main causes of variation
environment and genetic and combined (height, weight)
Standard deviation
how deviated it is from the mean, the bigger it is, the less accurate the data is = spread of data
Null hypothesis
there’s no statistically significant difference between the means of these two sets of data
T test
when you get your t value, take it to a statistical table. Degree of freedom = sample size - the number of data sets. Critical value = always is 5%. If t value is below the critical value, we accept the null hypothesis. If it’s above the critical value, we reject the null hypothesis.
Correlation coefficient
number of pairs of measurement instead of degrees of freedom. If the value is lower than the critical value then you accept the null hypothesis
Adaptation
a characteristic that can enhance survival, these adaptations can be how they look (e.g. long claws to climb), behavioural (any changes in behaviour), physiological (how their body processes work)
Real life examples of natural selection
- antibiotic resistance
- Pesticide resistance in insects
Pesticide resistance in insects
can move up the food chain and a higher dose of pesticide is needed to kill the insects which is harmful for us
How to know if two things should be classed as the same species?
- breed them together and see if offspring are fertile, if so they should be classed as the same species
Why are x and y still classified as same species:
- can produce fertile offspring
- Genetically similar
- Similar appearance
Synthetic biology
creation of an organism with an artificial genome
Ways scientists validate eachother research
- scientific meetings
- Peer review
- Replication of work
Why does a genetic bottleneck lead to low genetic diversity
- many alleles lost
- Modern population descended from few survivors
Why is genetic drift a concern in a small population
- one allele has proportionally higher affect on small population
- Alleles will be lost from population
- More likely to become extinct due to environmental change
Genetic drift
change in allele frequencies in population from generation to generation
Sympatric speciation
formation of two species from one original species due to reproductive isolation whilst occupying same location
Allopatric speciation
formation of two species from an original one due to geographical isolation
How can the same species w big beaks become reproductively isolated from itself w small beaks in the same location?
Individuals choose to mate only w other individuals w similar sized beaks
How can biological molecules provide evidence that species have evolved?
- DNA = two species dna sequence similarity can imply an evolutionary relationship
- Proteins = same protein from 2 species, amino acid sequence similarity implies evolutionary relationship
Likely causes of physical variation in species
- environment
- Many genes
- Age
How could evolution occur from a small species to a larger one (both still alive)
- Allopathic speciation
- Different environmental conditions
- Random mutation
- Individual w mutation reproduce + pass on beneficial allele
Conditions for speciation:
- reproductively isolated
- Genetic diversity
- Natural selection
- Selection pressure is diff from other population
How can two separate species both have evolved RHE same trait
- similar niche
- Similar selection pressure
- Idea that trait is advantage for survival in both so alleles for trait more likely to be passed to next gen
Why is some dna non coding
- not present in mature mRNA and not translated
Non coding dna shows more variation because…
Not selected against
