Evolution Flashcards
1
Q
sigmoid population growth curve
A
- 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
2
Q
reasons for lag - log - transition - plateau order
A
- 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
3
Q
list limiting factors to population increase
A
- availability of nutrients
- no of predators/parasites
- accumulation of waste
- disease
- shortage of space/territory
4
Q
evolution
A
the cumulative change in heritable characteristics of a population
5
Q
sub-theories of evolution
A
- 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
6
Q
evidence of evolution
A
- 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
7
Q
fossil formation processes
A
- 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)
8
Q
explain population tendency to produce more offspring than the environment can support
A
- 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
9
Q
consequence of overpopulation
A
struggle for survival; competition for limited resources
10
Q
variation in species
A
- 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
11
Q
sources of genetic variation
A
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
12
Q
sexual reproduction and variation
A
- 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
13
Q
how does natural selection lead to evolution
A
- individuals with favourable heritable variations have better survival and reproductive rates
- this influences the type of genes passed to the next gen
14
Q
natural selection stages
A
- 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
15
Q
examples of evolution in response to environment changes
A
- 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.
16
Q
factors affecting population size
A
- 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
17
Q
list 6 phyla
A
- Porifera
- Cnidaria
- Platyhelminthes
- Mollusca
- Annelida
- Arthropoda
18
Q
characteristics of Porifera
A
- 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
