5. Evolution Flashcards
Bryophytes
No xylem or phloem No leaves, roots or stems Reproduces via spores Anchored by rhizoids Ex: Mosses
Filicinophyta
Has xylem and phloem Has leaves, roots or stems Reproduces via spores Leaves are pinnate Ex: Ferns
Coniferophyta
Has xylem and phloem Has leaves, roots or stems Reproduces via seeds in cones Has woody stems Ex: pine trees
Angiospermopyta
Has xylem and phloem Has leaves, roots or stems Reproduces via seeds in fruits Has flowers and fruits Ex: Flowers
Definition of Evolution
The cumulative change in the heritable characteristics of a population over time
What are fossil records and what do they show
The totality of fossils- both discovered and undiscovered.
Provides evidence for evolution - shows a gradual change of species over time
Law of fossil succession
- Fossils can be dated by determining the age of the rock layer (strata) in which the fossil is found
- Sedimentary rock layers develop in chronological order
- Fossils show a chronological time sequence in which characteristics appear and develop in complexity
- Sedimentary rock layers develop in chronological order
Transitional fossils- what do they show, what are they evidence for
- Show links between species by exhibiting traits common to both ancestral species and its descendant species
- Ex: archaeopteryx - dinosaurs and birds
- Evidence for macroevolution- development of new species
- Ex: archaeopteryx - dinosaurs and birds
Selective Breeding- what is it and what does it show for evolution
When humans intervene to breed individuals with the most desirable traits
- Trait's frequency becomes more common in successive generations
- Evidence for evolution: targeted breeds show significant variation in a short period of time
- Accelerates evolutionary process
- Evidence for microevolution- changes within a species
- Shows that artificial selection can cause evolution
Homologous structures
- Definition
- Example
- Evidence for?
- Homologous Structures are similar shape in different types of organisms but have different functions
- Ex: Pentadactyl limb in vertebrates : same structure but adapted to different mode of locomotion in certain environment
- Evidence for adaptive radiation and divergent evolution
Define Divergent Evolution
When two separate species have a similar structure but use it in different ways because of their environment
Define Adaptive Radiation
Form of divergent evolution where many species evolve from a common ancestor to occupy a range of available niches
Analogous structures
- Definition
- Example
- Evidence for?
- Anatomical features performing a similar function but having a different evolutionary origin
- Ex: wings of insects and birds
- Evidence for convergent evolution
Define Convergent Evolution
Organisms that are not closely related evolve similar structures that are used for similar purposes
Speciation
- Definition
- How does it happen
- The evolutionary process by which two related populations diverge into separated species
- If two populations of a species become geographically separated, they will adapt to different environmental conditions and gradually diverge from one another
- As genetic divergence increases, genetic compatibility decreases
- When the two diverged populations meet again and cannot interbreed to produce fertile offspring, speciation has occurred
Explain industrial melanism example
Peppered moths- exist in two morphs/variations: light and dark form
- In an unpolluted environment, trees covered in lichen allowed light coloured moths to camouflage
- In a polluted environment (following industrial revolution), sulphur dioxide kills lichen and soot darkens bark, providing camouflage for dark coloured moths
- Frequency of the allele depends on the environment and evolves as conditions change
- Prior industrial revolution, light coloured moths had survival advantage, after industrial revolution, dark coloured moths did
- Pollution as natural selection pressure
Peppered moth would slowly diverge into two different species
Continuous variation
Type of variation controlled by many genes, has a wide range of variability and can be influenced by environment
Discontinuous variation
Type of variation that is influenced by genes, can be categorised, and is not influenced by environment
Steps of Natural Selection
- Genetic variation inherited
- Competition due to overpopulation for survival
- Adaptations- ‘survival of the fittest’
- Selection- successful inheritance of successful variations –> change in allele frequency –> evolution
Causes of variation
- Mutation - change in DNA base sequence
- Meiosis - crossing over and independent assortment
- Sexual reproduction - random fertilization
Types of adaptations
Structural i.e. neck length
Behavioral i.e. nocturnal
Physiological i.e. colour perception
Biochemical i.e. blood group
How do adaptations contribute to natural selection (in more detail)
Adaptations are characteristics that make an individual suited to its environment and way of life
- Individuals that are better adapted tend to survive and reproduce more offspring while the less adapted tend to die and produce fewer offspring
- leads to changes in the gene pool
How do natural selection pressures lead to speciation
Natural selection pressures –> adaptive radiation (from adaptations) –> divergent evolution –> speciation
Galapagos finches example
- Changes in beaks of flinches on the Galapagos islands
○ Specialised beak shapes depending on primary source of nutrition- Illustrates adaptive radiation
○ Members evolve different adaptations in response to the different selection pressures - Dry conditions –> larger seeds –> finches with larger beaks survive and reproduce –> allele frequency increases as offspring inherit large beak allele
- Illustrates adaptive radiation
Antibiotic Resistance example
- Bacteria reproduces and some can mutate- some of which causes resistance
- Resistant bacteria survives antibiotic treatment and reproduces by binary fission
- Resistant bacteria reproduce rapidly as competition eliminated by antibiotics
- Resistance bacteria develops and spreads easily with people
- Resistance can come from plasmid transfer of resistance-carrying genes
- Antibiotic (selection pressure) increases the antibiotic resistance gene frequency, bacteria susceptible to antibiotic dies –> evolution
Key words in example answer (natural selection)
- overproduction
- variation
- mutation (if relevant)
- environmental change/pressure
- survival of the fittest
- adaptation
- ‘passed onto offspring’
- change in gene pool
The binomial system
- The formal system by which all living species are classified (taxonomy)
- Universally agreed and developed by a series of congresses
Hierarchy of Taxa
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
3 Domains + differences
Bacteria- naked DNA, peptidoglycan cell wall
Archaea- Histones (in some), no peptidoglycan cell wall
Eukaryota- Histones, sometimes cell wall present, membrane-bound nucleus, one cell or more
4 Kingdoms of Eukaryotes
- Protista
- Fungi
- Plantae
- Animalia
What is natural classification
- A genus and accompanying higher taxa consist of all the species that have evolved from one common ancestral species
- Assumes all members of a particular group would have a shared common ancestor
Advantage and Disadvantage of Natural classification
- Advantages
○ Identifies traits based on groupings, rather than assigning groups based on traits
○ Can be used to predict characteristics shared by species within a group
○ Can show be used to show evolutionary relationships- Disadvantage
○ highly mutable and tend to change as new information is discovered
○ taxonomists can reclassify if new evidence shows a different ancestry or a new common ancestry
- Disadvantage
Porifera
Asymmetrical
No gut openings (has pores)
No segmentation
Use spicules for support
Sea sponge
Cnidaria
Radial
Mouth but no anus
No segmentation
Stinging cells
Jellyfish, coral
Platyhelmintha
Bilateral
Mouth but no anus
None segmentation
Flattened body
Tapeworm
Annelida
Bilateral
Mouth and anus
Segmented
Use peristalsis for moving
Leech, earthworm
Mollusca
Bilateral
Mouth and anus
Non-visible segmentation
May have shell made by mantle
Snail, octopus, squid
Arthropoda
Bilateral
Mouth and anus
Segmented
Exoskeleton (chitin)
Insects, spiders, crustacens
Fish
Scales
Fins
External
Gills
Ectothermic
Swim bladder
Amphibian
Moist skin
4 pentadactyl limbs
External
Simple lungs
Ectothermic
Larvae- water
Adult- land
Reptile
Scales made out of keratin
4 pentadactyl limbs
Internal - soft eggs
Lungs with extensive folding
Ectothermic
No external ears
Bird
Feathers
4 pentadactyl limbs + wings
Internal - hard eggs
Lungs with bronchial tubes
Endothermic
Wings
Beaks with no teeth
Mammal
Hair
4 pentadactyl limbs
Internal - live birth
Lungs with alveoli
Endothermic
Feed young with milk from mammary gland
Clade - definition
A group of organisms that have evolved from a common ancestor
Cladistics - definition
System of classifying organisms according to shared characteristics, based on ancestry
Cladogram - definition
(tree) diagram that shows the evolutionary relationship of a group of organisms
What is a node and what does it show
- where clades branch off
- where speciation has occurred; divergent evolution
- The fewer the number of nodes between two groups the more closely related they are expected to be
Where is evidence for a clade obtained from
- the base sequence of a gene or
- the corresponding amino acid sequence of a protein
Molecular clock
- Concept of using the mutation rate of biomolecules to deduce the time in prehistory when divergence happened
- But different genes/proteins may change at different rates, and differ between organisms, or changes may reverse over time
What part of the DNA sequence provide most information
Non-coding parts of DNA provide the most information as mutations occur more frequently in these regions than coding regions
How can structurally similar species be reclassified to be of different families
Molecular evidence show that species thought to be closely related based on shared structural characteristics actually have different evolutionary origins
