b5 - speciation/ classification Flashcards
species
a group of organisms which can interbreed to produce FERTILE offspring
a population can evolve into new species - this requires
ISOLATION
- geographical isolation
- reproductive isolation
how speciation occurs
- come from common ancestors
- a geographical barrier may form eg river
- species become geographically separate
- competition for resources drives adaptations
- the adaptions make organisms different so cant reproduce
- became so different females dont physically recognise males
- have been apart so long that mating rituals have changed
why is it important to have a clear definition of species
some species are dying out - we need to know what a species is to monitor individuals of a species + protect the species
peppered moth - evidence of evolution
- were more white moths due to camouflaged in sky
- was a mutant of black moths
- industrial revolution covered trees in soot
- more black moths as they were camouflaged
who came up with peppered moth theory + who proved it
James W Tutt
Bernard Kettlewell
what are fossils
fossils are remains of the existence of dead organisms
- sometimes traces of organisms are left (TRACE fossils)
- plants / insects sometimes trapped in amber
- trunks of trees found after being buried in mud containing volcanic ash
how are fossils formed
- organism dies in water
- covered in sediment
- soft parts decay
- pressure from above turns sediment to rock
- minerals replace body tissues to form rock - hard parts more likely to fossilise
why is oxygen not included in the fossilisation process
don’t want decomposers to cause decay
decomposers need O2 for respiration
fossils - evidence for evolution
- shows organisms that lived in the past differ from those today (have evolved)
why is the fossil record incomplete
- not all organisms fossilise
- are deep underground (uncovered by erosion or plate shift)
antibiotics
chemicals that kill bacteria
discovered 1928 - Alexander Flemming
antibiotic resistance
- there is variation
- mutation occurs
- few bacteria develops genes which make them resistant to antibiotics
- bacteria are exposed to antibiotic - most die
- more resources for resistant bacteria to multiply
- if the course of antibiotics completes all bacteria is killed
- if course incomplete the resistant bacteria thrive
- antibiotic is no longer effective
MRSA superbugs
a bacteria that is resistant to antibiotics
resistant rats
- there is variation
- a mutation causes resistance
- non resistant rats die and resistant survive/ reproduce
- pass on resistant gene
- over generations resistance gene increases
