Evolution Flashcards Preview

Biology IB HL > Evolution > Flashcards

Flashcards in Evolution Deck (45)
Loading flashcards...

sigmoid population growth curve

- lag phase as population adapts
- log phase (exponential phase) occurs when low limiting factors are present, allowing the population to expand exponentially (rate of natality/immigration > rate of mortality/emigration)
- linear growth phase (transition stage) occurs when resources are reduced and growth becomes limited, prompting lower rate of population growth
- stationary phase (population plateau) occurs when population remains constant over time


reasons for lag - log - transition - plateau order

- exponential growth phase: population has begun to grow and rises quickly due to low/negligible limiting factors and abundance of resources
- transitional phase: because limiting factors appear to slow the increase
- plateau phase: the habitat is supporting the max number of organisms at that time


list limiting factors to population increase

- availability of nutrients
- no of predators/parasites
- accumulation of waste
- disease
- shortage of space/territory



the cumulative change in heritable characteristics of a population


sub-theories of evolution

- evolution: all life is perpetually changing
- common descent: all living things share a common ancestor
- gradualism: evolution change takes place slowly and gradually
- multiplication of species: diversity of life is a consequence of speciation due to populations adapting to locations and becoming isolated
- natural selection: a two-step process involving genetic variation and selection of the most suitable


evidence of evolution

- fossil records: fossils are ancient remains of organisms preserved through rare events. their age can be determined via carbon dating.
- homologous structures: show all life is connected and contain traits from a common ancestor
- selective breeding: useful characteristics in an organism lead to selection for breeding - these characteristics will be present in the next generation in higher frequency


fossil formation processes

- petrification: organic matter is replaced by mineral ions
- mould: organic matter decays and the space becomes a mould
- trace: impression (footprint etc) hardens in the layers
- preservation: the organism is preserved (e.g. in amber or anaerobic+acidic peat)


explain population tendency to produce more offspring than the environment can support

- chances of survival increase for the whole population
- increased population causes competition for limited resources
- organisms with better characteristics are more likely to reproduce, causing the characteristics to be more frequent in the next generation


consequence of overpopulation

struggle for survival; competition for limited resources


variation in species

- all members of a species will show variation/difference in phenotypes
- discontinuous variation: when there are distinct classes of individuals
- continuous variation: no distinct classes but complete range of characteristics


sources of genetic variation

mutated gene: can be beneficial, harmful, lethal, or no effect. it can occur in both asexual and sexual reproduction. migration can cause genes that were not previously present to appear in later generations


sexual reproduction and variation

- meiosis and the independent assortment of chromosomes creates 2^n new combination of chromosomes in the next gen (n = haploid no of chromosomes)
- random fertilisation increases variation to 2^2n
- haploid gametes are unified during fertilisation, leading to increased variation to 2^3
- so the no of genetic variations is 2^n x 2^2n x 2^3
- so sexual production gives rise to greater variation


how does natural selection lead to evolution

- individuals with favourable heritable variations have better survival and reproductive rates
- this influences the type of genes passed to the next gen


natural selection stages

- overproduction: organisms have more offspring than the environment can support
- variation: mutations, random assortment of chromosomes, and random fertilisation lead to continuous variation
- competition: limited resources means not all individuals will survive
- survival of the fittest phenotype: individuals with more beneficial characteristics will have an advantage in survival and reproduction
- increase in frequency of favourable genes


examples of evolution in response to environment changes

- staphylococcus aureus: bacteria associated with skin and lung conditions. it adapted to the use of antibiotics and has developed to be resistant to the antibiotic methicillin
- New Zealand kaka: was isolated from parrot ancestors by the Tasman sea. when NZ became more alpine, selection pressure increased and two species developed: the alpine kea and lowland kaka. NZ then split into 2, causing further divergence to produce the north island kaka and South Island kaka.


factors affecting population size

- natality: as birth rate increases, population increases (exponential)
- immigration: arrival of organisms to the population from another area
- mortality: death rate increases as population increases
- emigration: departure of organisms from the population to another area

a population is stable when:
natality + immigration = mortality + emigration


list 6 phyla

- Porifera
- Cnidaria
- Platyhelminthes
- Mollusca
- Annelida
- Arthropoda


characteristics of Porifera

- mouth/anus: none
- symmetry: none
- skeleton: skeletal needles (internal spicules)
- other external features: many pores to draw water in for filter feeding; varied shapes of organisms
e.g. tube sponges, fan sponges, cup sponges


characteristics of Cnidaria

- mouth/anus: mouth only
- symmetry: radial
- skeleton: soft, but hard corals secrete CaCO3
- other external features: tentacles in rings around mouth, stifling cells; polyps or medusae
e.g. jellyfish, coral, anemone


characteristics of Platyhelminthes

- mouth/anus: mouth only
- symmetry: bilateral
- skeleton: soft, no skeleton
- other external features: flat and thin bodies like a ribbon; no blood system or gas exchange system
e.g. tapeworm, flatworm


characteristics of Mollusca

- mouth/anus: both
- symmetry: bilateral
- skeleton: most have CaCO3 shells
- other external features: mantle (fold in body wall) to secrete shell; hard rasping radula for feeding
e.g. snails, squid, octopus, gastropod


characteristics of Annelida

- mouth/anus: both
- symmetry: bilateral
- skeleton: internal cavity with fluid under pressure
- other external features: bodies made up of many ring-shaped segments, often with bristles; visible blood vessels
e.g. leeches


characteristics of Arthropoda

- mouth/anus: both
- symmetry: bilateral
- skeleton: external skeleton made of plates of chitin
- other external features: segmented bodies and legs or other appendages with joints between sections
e.g. insects, arachnids, crustaceans, myriapods


classes of chordate

- bony fish
- amphibians
- reptiles
- birds
- mammals


characteristics of bony fish

- scales: bony plates in the skin
- gills covered by an operculum, with one fill slit
- no limbs
- fins supported by rays
- external fertilisation
- remains in water throughout life cycle
- swim bladder containing gas for buoyancy
- cold-blooded


characteristics of amphibians

- soft moist skin permeable to water and gases
- simple lungs with small folds and moist skin for gas exchange
- tetrapods with pendactyl limbs
- 4 legs
- external fertilisation
- larval stage in water; adult on land
- eggs coated in protective jelly
- cold-blooded


characteristics of reptiles

- impermeable skin covered in keratin scales
- lungs that have extensive folding (high surface area)
- tetrapods with pentadactyl limbs
- 4 legs (mostly)
- internal fertilisation
- eggs have soft shells
- one type of teeth only, with no living parts
- cold-blooded


characteristics of birds

- skin with feathers of keratin
- lungs with para-bronchial tubes ventilated with air sacs
- tetrapods with pentadactyl limbs
- 2 legs and 2 wings
- internal fertilisation
- hard shelled eggs
- beak (no teeth)
- warm blooded


characteristics of mammals

- skin has follicles with hair made of keratin
- lungs with alveoli, ventilated using ribs and diaphragm
- tetrapods with pentadactyl limbs
- 4 legs in most, or 2 legs and 2 wings/arms
- internal fertilisation
- mostly give birth to live young
- mammary glands with milk
- warm blooded


name the plant phyla

- Bryophyta
- coniferophyta
- angiospermophyta
- filicinophyta