Topic 4: Evolution + Classification ❀ Flashcards
Why are organisms put into classifications?
-To identify species
-Predict characteristics
-Find evolutionary links
Three domains for classification (start of classifications)
Domains:
-Archae
-Bacteria
-Eukarya
Process of classification
Process of classification:
-As you move down the hierarchy there are more groups at each level and fewer organisms in each groups
-Organisms within a group become more similar and share more characteristics
Taxonomic groups (KPCOFGS)
Kingdom
Phylum
Class
Order
Family
Genus
Species
What was the original way organisms were named?
Organisms were originally named based on how they look or their behaviour, but this was not ideal for international scientists so it has since changed
How are organisms named now? (Bionomial nomenclature)
Organism names:
1st part - genus (1st letter capitalised)
2nd part - species (1st letter lower cap)
+always written in italics on computer or underlined if handwritten
Intraspecific variation
Intraspecific variation is variation among individuals of the same species
The 5 kingdoms
The 5 kingdoms:
-Prokaryotae (bacteria)
-Protoctista (unicellular eukayotes)
-Fungi (yeasts/moulds/mushrooms etc)
-Plantae (plants)
-Animalia (the animals)
Why were organisms originally classified into kingdoms?
Organisms were originally classified into kingdoms based on similarities in their observable features
General features of prokaryotae
General features of prokayotae:
-Unicellular
-No nucleus or other membrane-bound organelles
-No visible feeding mechanism - nutrirents absorbed through cell wall or produced internally by photosynthesis
General features of protoctista
General features of protoctista:
-(Mainly) unicellular
-Nucleus and other membrane-bound organelles
-Some have chloroplasts
-Some are ssesile, but others move by cillia, flagella or by amoeboid mechanisms
-Nutrients acquired by photosythesis (autotrophic feeders), ingestion of other organisms (heterophic feeders) or both - some are parasitic
Autorophic feeders
Autorophic feeders make their own food - eg acquire nutrients by photosynthesis
Heterophic feeders
Heterophic feeders are where nutrients are acquired by ingestion - eg ingest other organisms
Parasitic
Parasitic - acquire nutrients both by photosynthesis and ingesting other organisms (autotrophic + heterophic)
Fungi general features
Funi general features:
-Unicellular or multicellular
-A nucleus an dother membrane-bound organelles and a cell wall mainly ocmposed of chitin
-no chloroplasts or chlorophyll
-No mechanisms for locomotion
-Most have a body or mycelium made of threads or hyphae
-Nutrients are acquired by absorption - mainly from decaying materials (sprophytic feeders), but some are parasitic
-most store their food as glycogen
Saprophytic feeders
Saprophytic feeders absorb nutrients from decaying material (eg fungi)
General plantae features
General plantae features:
-Multicellular
-A nucleus and other membrane-bound organelles including chloroplasts, and a cell wall mainly composed of cellulose
-All contain chlorophyll
-Most don’t move, though gametes of some plants move using cilia or flagella
-Autotrophic feeders
-Store food as starch
General animalia features
General animalia features:
-Multicellular
-Nucleus and other membrane-bound organelles (no cell walls)
-No chloroplasts
-Move with the aid of cilia, flagella, or contractile proteins sometimes in the form of muscular organs
-Heterotrophic feeders
-Food stored as glycogen
How are organisms classified now?
Organisms are classified by evolutionary links between organisms. This is done by comparing similiraties in DNA and proteins of different species
Current classification system
Current classification system is the ‘Three DOmain System’ - proposed by Carl Woese in 1977
How does the Three Domain System group organisms?
The three domain systems groups organisms using diferences in the sequences of nucleotides in the cells rRNA as well as the cells membrane lipid structure and their sensitivity to antiobiotics
The three domains
The three domains are Archae, Bacteria, Eukarya
RNA and ribosomes of eukarya
Eukarya - 80s ribosomes, RNA polymerase contains 12 proteins
RNA and ribosomes of archae
Archae: 70s ribosomes, RNA polymerase of different organisms contains between 8 and 10 proteins and is very similar to eukaryotic ribosome
RNA and ribosomes of Bacteria
Bacteria - 70s ribosomes, RNA polymerase contains 5 proteins
6 kingdoms of the current ‘Three Domain System’ model (Woese’s system)
6 kingdoms: archaebacteria, eubacteria, protocista, fungi, plantae, animalia
Why is eubacteria classified into their own kingdom different from archaebacteria despite both being single-cells prokaryotes?
Eubaceria has a different chemical makeup from archaebacteria. They contain peptidoglycan (a polymer of sugars and amino acids) in their cell wall wheras Achaebacteria do not
Archaebacteria
Archaebacteria live in extreme environments eg hot thermal vents, anaerobic conditions (eg methanogens) and highly acidic environments
Eubacteria
Eubacteria (also known as true bacteria) are found in all environments
Phylogeny
Phylogeny = name given to the evolutionary relationships between organisms
Phylogenetics
-Phylogenetics is the study of the evolutionary history of groups of organisms
-Reveals which group a particular organism is related to and how closely related these organisms are
Phylogenetic trees
Phylogenetic trees - diagrams used to represent the evolutionary relationships between organisms
-Branched diagrams shows that different species have evolved from a common ancestor
-Earliest organisms found at base
How are phylogenetic trees produced
Phylogenetic trees are produced by looking at similarities and difference sin species physical characterics and genetic makeup
Advantages of phylogeny
Advantages pf phylogeny
-Can be done without reference to the linnaean classification system
-Produces continuous trees wheras classification requires descrete taxonomical groups
-Hierarchal nature of linnaean classification can be misleading
Evolution definition
Evolutoin - the theory that describes the way in which organisms evolve, or change, over many years as a result of natural selection
Evidence for evolution
Evidence for evolution:
-Uniformitarianism
-Palaeontology
-Comparative anatomy
-Comparative biochemistry
Uniformitarianism
Uniformitarianism: evolution is a slow process where changes gradually accumulate over long periods of time
Palaeontology
Palaentology: study of fossils and fossil record - simple organisms found in oldest rocks, more complex found in more recent rocks
- sequence of fossils matches ecological links (plants before animals)
- similarities between anatomy of fossils alows scientists to see how closely related organisms are and how they have evolved from a common ancestor
Comparative anatomy
Comparative anatomy: study of the similarities and difference between organisms anatomy
Comparative anatomy - homologous structure
A homologous structure is a structure that appears superficially different in different organisms but has the same udnerlying structure
What does the presence of homologous structures provide evidence for?
The presence of homologous structures provide evidence for divergent evolution
Divergent evolution definition
Divergent evolution: describes how, from a common ancestor, different species have evolved, each with a different set of adaptive features
Comparative biochemistry
Comparative biochemistry:
-Similarities and differences between the chemical make-up of organisms
-Most molecules are highly conserved among species - eg cytochrome c in respiration
-Slight changes that occur can help identify evolutionary links
Two most common molecules studied in comparative biochemistry
Most common molecules studied in comparative biochemistry: cytochrome c (protein involved in respiration) and ribosomal RNA
Neutral changes
Neutral changes do not affect a molecule’s function
How do you discover how closely related 2 species are?
Discover how closely related 2 species are by comparing the molecular sequence of a particular molecule
How is the number of differences between species plotted in comparative biochemistry?
The number of differences between species is plotted against the rate the molecule undergoes neutral base pair substitutions
-Scientists can use this to pin point when two species last shared a common ancestor
3 Scientists involved in the development of the theory of evolution
3 scientists:
-Darwin = proposed the idea of natural selection
-Lyell = suggested fossils was best evidence of past organisms
-Hutton = proposed theory of uniformitarianism
Interspecific variation
Interspecific variation: variation between members of different species
Causes of variation
Causes of variation:
-Genetic variation
-Environmental variation
Causes of genetic variation
Causes of genetic variation:
-Alleles (different characteristics)
-Mutations (changes in DNA sequence)
-Meiosis (independant assortment)
-Sexual reproduction (offspring from parents inherits genes from both parents)
-Chance
Discontinuous variation
Discontinuous variation: qualitative differences in the phenotypes of individuals within a population (distinctive categories) - determined purely by genetic factors (a single gene - polymorphic gene-)
eg blood type
Continuous variation
Continuous variation: quantitative differences in the phenotypes of inidividuals within a population for particular characteristics (no distinct characteristics - measured within a range between two extremes) -environmental + genetic factors (more than one gene )
eg height and mass
Characteristics of normal distribution
Characteristics of normal distribution:
-Mean, median and mode are the same
-Bell shape which is symmetrical to mean
-50% values less than mean, 50% greater than mean
-Most values lie close to mean value - number at extremes are low
Standard deviation
Standard deviation is a measure of how spread out the data is (high standard deviation = large amount of variation)
Spearmans rank
Spearmans rank shows correlation coefficient
Positive correlation = as one increases, the other increases
Negative correlation = as one increases, the other decreases
No correlation = no relationship between data
Adaptations categories
Categories of adaptation:
-Anatomical adaptation (physical features)
-Behavioural adaptation
-Physiological adaptation (processes that take place within the organism)
Anatomical adaptation examples
Body covering, camouflage, teeth, mimicricy
Xerophytes
Xerophytes are plants that are adapted to live in an environment with little water by reducing transpiration rate
Marram grass (xerophyte) adaptations to reduce transpiration
Transpiration loss adaptations:
-Curled/rolled leave to minimise sa of moist tissue exposed to air
-Hairs on inside surface to trap moist air
-Stomata sunk into pits so less likely to open
-Thick waxy cuticle to reduce evaporation
Examples of behavioural adaptation
Behavioural adaptations:
-Surivival behaviours (eg playing dead)
-Courtship (attracting mates)
-Seasonal behaviours (migration, hibernation)
2 main categories of behavioural adaptations
2 main categories of behavioural adaptations:
-Innate (instinctive) behaviour: inherited through genes - surviving their habitat
-Learned behaviour - from experience
Physiological adaptation examples
Physiological adaptation examples:
-Poison production
-Antibiotic production
-Water holding
Analogous structures
Analogous structures - structures that carry out the same function but have a different genetic origin (eg tail fins of a whale and of a fish)
Convergent evolution
Convergent evolution = when unrelated species begin to share similar traites due to adaptations to a similar environment
How to read standard deviation on bar charts
-2 standard deviations plotted, if bars overlap it is likely due to chance, if they don’t overlap it is unlikely that it is due to chance
How do we know wether to accept or reject the null hypotheses? (spearmans rank)
If the spearman’s rank correlation coefficient is smaller than the critical value = accept the null hypothesis
If it is bigger than the critical value, = reject the null hypothesis
Selection pressure
Selection pressures are factors that affect the organism’s chances of survival or reproductive sucess
Steps of natural selection
Steps of natural selection:
-Genetic variation in species
-Organisms adapt their characteristics to selected pressures ie predation are more likely to survive
-Those organisms pass allele which encodes the advantageous characteristic onto offspring
-Repeated for every generation
-Can lead to evolution of new species overtime
Cacti adaptations
Cacti adaptations:
-Replaces leaves with spines to reduce surface area to volume ratio to reduce water loss
-Spines trap moist air near cacti to reduce transpiration + provide shade (less heat > less evaporation)
-Thick waxy cuticle reduces evaporation
-Stomata stunk into pits - traps moist air around stomata + stomata opens at night to allow co2 in for photosynthesis in daytime
-stores water in stem (succulent)
Marram grass adaptations
Marram grass adaptations:
-Leaves rolled into tubes with stomata inside - moist air trapped within
-Stomata in sunken pits to trap air and fine hairs project inwards > reduces concentration gradient for water vapour > reduces diffusion out stomata
-Thick waxy cuticle
-Long roots
Why can organisms still be considered the same spiecies even when isolated?
-Fertile offspring
-Genetic similarities
-Not enough phenotype differences (still similar in appearance)
Why might the measurement of biodiversity in an area be inaccurate/lower than real amount?
-Inaccurate sampling of the area
-Camouflaged organisms
-Not all of the area explored
Classifying organisms into the same species
Same species if:
-Can produce fertile offspring together
-Similar physical structures
-Similar genetics
-Same functioning in the wild
Why do scientists classify organisms?
Scientists classify organisms to:
-Identify species
-Predict characteristics
-Find evolutionary links
Defining species
Species is defined as a group of organisms that are able to reproduce fertile offspring
What are the new classification systems based on now that technology has advanced?
Classification systems now are based on the DNA sequences and proteins of organisms. Closely-related organisms have DNA with a more similar base sequence and proteins with a similar amino acid sequence
Modern techniques used to establish evolutionary relationships between species
Modern techniques used to establish evolutionary relationships between species:
-Genome sequencing
-Antibody-Antigen interactions
-Amino acid sequencing
How is genome sequencing used to establish evolutionary relationships between species?
Genome sequencing:
-Base sequences of organisms sequenced and compared to other organisms
-More similar the base sequence = more closely related
How is antibody-antigen interactions used to establish evolutionary relationships between species?
Antibody-antigen sequencing:
-Species produce specific antibodies that recognise foreign proteins - antibodies can be isolated and mixed with other organism’s proteins to see how many antigen-antibody complexes form
-More complexes = more closely related
How is amino acid sequencing used to establish evolutionary relationships between species?
Amino acid sequencing:
-Amino acids can be sequenced and compared to other organisms
-More similar the amino acid sequence = more closely related
-Eg cytochrome C (used in respiration) can be used to compare organisms
DNA that can be used to compare evolutionary relationships between organisms
We can used mitochondrial DNA, chloroplast DNA as well as chromosomal DNA to compare organisms
Convergent evolution
Convergent evolution - organisms showing similarities in anatomy despite not being closely related - features evolve independently in places where selection pressures are similar
Implications of evolution on humans
Implications of evolution:
Bacteria/Microorganisms are becoming resistant to antibiotics > increased risk of disease spread
+ Pests are becoming resistant to pesticides - reduces farmer yields - effects future food security + finances
Development of antibiotic resistance
Development of antibiotic resistance:
1) Bacteria within the population randomly mutate to become resistant > humans take antibiotics
2) Non-resistant bacteria die, whilst those resistant survive
3) Resistant bacteria reproduce rapidly as competition is killed
4) Lots of genetically-identical copies of resistant bacteria produced
What year did Charles Darwin and Alfred Wallace publish ‘On the origin of species’ together?
On the origin of species was published in 1858
How do you find out if your result is statistically significant or not?
-Look up your result in the Student’s t test significance tables.
-First, calculate a quantity know as the ‘degrees of freedom’ (df) using the formula: (n₁ + n₂) - 2
-Then look at the corresponding probability values. For the data to be considered significantly different from chance alone, the probability must be less than 0.05.
