Biology Unit 2
- Created by: slr674
- Created on: 20-11-14 18:21
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- Biology Unit 2
- New Species
- Speciation is formation of NEW species
- Could become separated geographically
- e.g. Move to different islands, the environment between them changes, so can't cross it
- Natural selection takes place
- = different variations of characteristics favoured
- characteristics of population change
- Characteristics so different, individuals from different populations can't interbreed, even if were in same area
- = DIFFERENT species!
- Characteristics so different, individuals from different populations can't interbreed, even if were in same area
- Extinction
- All individuals of a species dies out
- CAUSES
- Disease
- Competitors e.g. take food/resources
- New predators
- Catastrophic event
- e.g. asteroid or massive volcano erruption
- Changes to environment over millions of years
- organisms cannot adapt fast enough
- GEOLOGICAL TIME
- Fossils
- remains from organisms from many years ago, found in rocks
- Formation
- Dead organisms decay
- 1.Hard parts don't decay easily, so fossilise
- e.g. teeth and bones
- 2.Conditions don't allow decay e.g. not enough oxygen
- Soft tissues also fossilise e.g. leaf, muscle tissue, animals with no hard parts
- 3.Parts of organisms replaced by other materials as decay
- 1.Hard parts don't decay easily, so fossilise
- traces of organisms fossilise in special conditions
- e.g. footprints as casts in mud
- Dead organisms decay
- age figured out by age of rock, can show how much organisms changed over millions of years
- record not completed because...
- 1.they only form in special conditions
- 2.many early life forms had soft bodies, so left few traces
- 3.geological changes in rock = destroys fossils
- Embryo screening
- people who think they have allele from inherited disorder can have embryo screened at early stage of pregnancy
- Issues
- Economic
- may cost parents extra money to support child with disorder
- would child need lot of hospital treatment/drugs?
- Social
- who will care for child if parents can't?
- If needs lots of care, is it fair on other children in family?
- Ethical
- embryo has same right to life as person
- Screening carries small risk of damaging embryo - should risk be taken?
- Economic
- Family trees
- Can inherit allele for a disorder
- Cystic Fibrosis disorder affects cell membranes, makes mucus stickier than normal
- F = dominant allele and f = recessive allele
- Ff are CARRIERS
- ff is cystic fibrosis
- FF doesn't have it, can't pass it on
- Caused by RECESSIVE allele
- Punnet squares
- Polydactyly= condition of having more than 5 toes or five fingers
- DD=polydactyly
- Dd=polodactyly
- dd=normal
- Caused by DOMINANT allele
- Mendel's work
- studied inheritance of many characteristics in pea plants
- 1.published work =1865 2. died=1884 3. later work by other geneticists linked Mendel's "inherited factors" to genes and chromosomes
- 1.spent several years producing PURE-BREEDING plants
- produced same characteristics every time when bred with each other
- 2. made the crosses by hand, so could be certain which parents produce offspring
- 3.repeated each test 100s of times
- New Species
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