B14 Variation and Evolution Flashcards
What is Variation?
The difference in the characteristics of an individual in a population
What are reasons for variation?
- Genetic causes (differences in inherited genes: eye colour, sex)
- Environmental causes (conditions an organism develops in: plants grown in light, deprived of co2 or mineral ions)
- Combination of both (Environmental + Genetic causes: inherited hair and skin colour, get bleached or darker skin from sun)
What are the only type of genetically identical humans?
Identical twins- from the same fertilised egg
What is Natural Selection?
Organisms gaining an advantage over members of their own species through mutation, making them more likely to breed and survive
What is a phenotype?
the physical characteristics of an organism
What is the theory of evolution by natural selection?
All species of living things have evolved from simple life forms that first developed over 3 billion years ago
When do mutations occur?
Occur continuously, can take place when cells divide
What happens if a mutation takes place when gametes are formed?
- Affect phenotype, introduce new variants into genes of species (important for survival)
- Mutations can have no effect on phenotype, can also be fatal
- Mutations RARELY produce adaptations making organisms better suited to their environments/ give advantages if there is an environmental change
How can evolution result in organisms well suited to their environments ?
- individual organisms within a particular species may show a wide range of phenotype and genetic variation
- those with characteristics best suited to the environment are more likely to survive + breed successfully
- the alleles (variants) enabling the individuals to survive is passed onto offspring
When can a population of species evolving through natural selection be named a different species to another population of the same initial species?
If 2 populations of 1 species become so different they can no longer interbreed to produce fertile offspring, they have formed 2 new species
What is Selective Breeding?
The process where humans breed plants and animals for desired characteristics
What is the process of selective breeding?
- Farmers + breeders select animals and plants from mixed populations that have useful or desirable traits- they are their breeding stock
- then select offspring and only breed from the ones that show desired characteristics
- continues over generations until all offspring show desired characteristic
What are examples of desired characteristics?
- disease resistance (plant)
- animals producing more meat, milk etc (food produce)
- domestic dogs and farm animals with gentle nature
- bright, large, unusual or heavily scented flowers
What are some problems with Selective breeding?
- reduces number of alleles in population (only individuals with specific alleles are allowed to breed)-> reduces variation, can result in population dying out if the environment changes (new disease, climate change)
- Can results in inbreeding-> little variation in population, prone to diseases + inherited defects
What is genetic engineering?
Modifying the genetic material of an organism to give it more desirable characteristics
What is the process of genetic engineering?
- enzymes are used to isolate and take the required gene from an organism
- gene is then inserted into a vector using more enzymes (ie bacterial plasmid or virus)
- vector is then used to insert gene into required cell (bacteria, animal, fungi or plants)
- genes transferred to cells at early stage of development (ie egg or early embryo in animals).
Organism grows, develops new desired characteristics from other organism
How are plants usually genetically engineered?
Desired genes often inserted into meristem cells-> used to produce identical clones of genetically modified plant
What are examples of transferring genes to animal and plant cells?
- Genetically engineered bacteria can be cultured on a large scale-> make huge quantities of protein for other organisms (Ie human insulin, human growth hormone)
- genes from jellyfish-> produce glow in the dark crops
- animals make human proteins in their milk
- modified mice to model human diseases (Alzheimer’s, cancer, diabetes)
What are GM crops?
Crops that have had their genes modified by genetic engineering techniques
(genetically modified crops)
What are characteristics of GM crops?
- often show increased yields-> improved resistance to insect attacks
- more resistant to herbicides-> farmers can spray + kill more weeds without damaging plants (increase crop yield)
- increase size of fruit or nutritional value of the crop
Why is increasing crop yield important? + examples
provides food security for world’s human population
- modified potatoes to make more starch + be more resistant to several common pests
- modified soy beans-> produce healthier balance of fatty acids
- Golden rice filled with nutrients
- resistant to common diseases (ie mosaic virus)
What is a clone?
an individual that has been produced asexually and is genetically identical to the parent
Why are certain animals and plants chosen to be cloned?
High quality characteristics
- resistance or high milk yield etc
What do clones have identical genetic information to?
- to each other
- to the single parent nucleus
