variation and extinction Flashcards
what is tissue culture
this is where a few plant cells are put in a growth medium with hormones and they grow into clones of the parent plant
what is tissue culture used for
- to preserve rare plants that are hard to reproduce naturally
- by plant nurseries to produce lots of stock quickly
what do cutting do
they produce genetically identical copies of each parent plant
pros of cuttings
plants can be produced quickly and cheaply
how do you make animal clones
by using embryo transplants
adult cell cloning
how do embryo transplants work
1) sperm cells are taken from the male animal and egg cells are taken from the female animal
2) the sperm is then used to artificially fertilise an egg cells and the embryo that develops is then split many times to form clones before any cells become specialised
3) these cloned embryos can be implanted into lots of other female animals where they grow into babies which will all be genetically identical to each other
how does adult cell cloning work
1) you take an unfertilised egg cell and remove its nucleus
2) then another nucleus is then removed from an adult body cell and is inserted into the egg cell
3) the egg cell is then stimulated by an electric shock, making it divide
4) when the embryo is a ball of cells its implanted into the womb of an adult female and grows into a genetically identical copy of the original adult body cell as it has the same genetic information
what technique was used for the clone sheep dolly
adult cell cloning
cons of cloning
- it reduces the gene pool, reducing variation making the whole population more prone to being wiped out by a disease as there may not be an allele in the population to give resistance to the disease
- cloned animals may not be as healthy as notmal ones
- may lead to humans being cloned in the future with disabilities
pros of cloning
- could lead to a greater understanding of the development of the embryo and ageing of age-related disorders
- could help preserve endangered species
what are fossils
the remains of organisms from many thousands of years ago
what do fossils show
how much or how little an organism has changed over time
3 ways fossils were formed
1) from the gradual replacement by minerals
2) from casts and impressions
3) from preservation in places where no decay happens
how were fossils formed from GRADUAL REPLACEMENT BY MINERALS
1) things that dont decay easily e.g teeth can last a long time when buried
2) they are eventually replaced by minerals as they decay, forming a rock like substance
3) the surrounding sediment also turns to rock but the fossils stay distinct inside the rock and eventually someone digs them up
how were fossils formed from CASTS AND IMPRESSIONS
1) the fossils that formed when an organism is buried in a soft material e,g clay hardens around it and the organism decays, leaving a cast for itself
2) footprints can be also pressed into these material when soft leaving an impression
how were fossils formed from PRESERVATION IN PLACES WHERE NO DECAY HAPPENS
1) n amber ( a clear yellow stone) and tar pits there is no oxygen or moisture so decay microbes cant survive
2) in glaciers its too cold for decay microbes to work
3) peat bogs are too acidic for decay microbes
why cant hypotheses of the foramtion life be accepted
as there is no evidence to support it since
- many early forms of life were soft bodied and many soft tissue tends to decay away completely so the fossil record is incomplete
- fossils that did form millions of years ago may have been destroyed by geological activity
what are species
a group of similar organisms that can reproduce to give fertile offspring
