Domestication of Animals and Crops Flashcards
The four great discoveries of Prehistory
- Tool
- The control of fire
- The invention of the wheel
- The invention of agriculture
What size groups did hunter-gatherers live in?
30-60 individuals
When was the shift from hunter-gatherer to farmers?
11,000 BC to 1,500 BC
Cause of shift to agricultural lifestyle
- Decline in the availability of wild foods
- Depletion of wild game so less rewarding, easier to gather grain
- Increased technology for collecting, processing and storing wild foods
- Adopt food production or die at the hands of those who have
What is the paradox when populations turned to agriculture?
The height and health of people generally declined
What is a crop?
Any organism that is harvested by another
What is a cultivated crop?
Plants or animals grown via human interference
What is a domesticated organism?
Plant or animal brought into the household. Humans often interfere with the reproductive process leading to fundamental genetic changes - these domesticated organisms are different to the wild type
What did the transition from wild to cultivated to domesticated involve?
- Gigantic characteristics
- A reduction/increase in fertility
- A loss of survival characteristics
- Loss of harmful substances
- Loss of protective structures
- Loss of delayed germination
- Early and simultaneous ripening
- Changes in organ shape
- Increase in rate of self-pollination
What is the FOXP2 gene?
- The first language gene discovered
- Winged helix/forkhead class of transcription factors
- Expressed in multiple tissues and has high level of expression in fetal brain
- This gene allows humans to use such elaborate communication
- Highly conserved, only 3 amino acid differences between humans and mice
What is the nucleotide diversity between humans?
0.1-0.4%
What is the nucleotide diversity between humans and chimpanzees?
1.2%
What is the gene MYH16?
One of several myosin heavy chain genes involved in skeletal muscle formation. The mRNA of the gene is expressed specifically in jaw muscles. High levels of the protein are found in the jaw of primates but not humans. During human evolution, there was a 2 base our deletion leading to frameshift, resulting in a non-functional gene, which is why humans have a much smaller jaw than primates
Where did pig domestication occur?
Central Europe, Italy, Northern India and South East Asia, possibly all independently
Features of wild boar
48kg
Fat area of 12.6 cm squared
Aggressive and difficult to farm
Features of meishan pig
82kg
Fat area of 24.4 cm squared
Domesticated pig bred to provide lots of useful fats for human use
Features of pietran pig
117 kg
Fat area of 15.9 cm squared
Domesticated pig bred for lean meat
What is the IGF2 gene?
Expressed in prenatal meishan, pietran and wild boar, and helps to form skeletal muscle. In meishan pigs and wild boar, it is only expressed weakly after birth, but in pietran pigs it continues to be strongly expressed after birth. This is due to a silences that prevents further expression of the gene mutating so it can no longer bind to the gene
What is polyploidy?
A major mechanism in plant evolution, involving the generation of a chromosome number which is a multiple of some ancestral set - the organism becomes tetraploid rather than diploid
How does polyploidy occur?
I’ve either abnormal meiotic (non-disjunction) or mitotic division
What is the benefit of tetraploid wheat?
It has two grains per floret rather than one so has much higher yield
What was the development of the rachis in the domestication of wheat?
The spiklets of wild (diploid) ears fall apart at ripening through fragmentation of the rachis by shattering. However, the tetraploid forms have a tough rachis that holds the seeds together in a harvestable ear
What was the old method of removing the chaff (casing) from the seed?
Parching
Heating the grains by holding them over a fire. It is slow and tedious.
Threshing could not successfully remove the chaff from grains, because the grain was held too tightly by the chaff
How is the chaff removed from the seeds of domesticated tetraploid wheat?
Free-threshing
These organisms have a mutation called the Q gene which produced a free-threshing wheat, making the separation of the grain from the chaff easy
What does free-threshing preserve?
Gluten. As it is a protein, heating destroys the gluten in wheat flour. Leavened bread cannot be made without gluten
What form of polyploidy is seen in current bread wheat?
Hexaploidy - even greater yield
What is genetic erosion?
The loss of genetic variation via a reduction in the size of the gene pool
What are molecular markers used for?
Pieces of DNA randomly places in the chromosome, used in breeding programmes to follow genes or which the phenotype is difficult to score. The molecular marker must be closely linked to the gene of interest
What is a strong selective sweep?
It results in a region of the genome where the advantageous new allele is essentially the only one that exists in the population, resulting in a large reduction in the total genetic variation in that chromosome region
What is the dangerous result of a selective sweep?
There is homozygosity not only at the locus of the specific gene, but also at flanking loci owing to ‘hitch-hiking’. The flanking alleles can be ‘bad’ alleles and have a dangerous effect on the carrier
What is porcine stress syndrome?
In pigs, there is a gene linked to the IGF2 gene (determines leanness) called RYR1. One allele of this gene is mutated, and if pigs which are homozygous for this gene are subjected to stress or anaesthetic, they die of malignant hypothermia. Pietran pigs with a mutated silencer are homozygous for this gene
What has been the main cause of genetic erosion in domesticated species over the last 100 years?
The release of modern cultivars
Advantages of modern cultivars (monocultures)
- Uniform product
- Required less farmer input time
- Suitable for big business input
Disadvantages of modern cultivars (monocultures)
- Susceptible to change in circumstances (low genetic diversity)
- Requires high input (fertiliser, pesticides, etc)
- Less suitable for small farmers
What proportion of world cereal is fed to livestock?
over 1/3
When was Dolly the cloned sheep born? How many attempts were made to clone a sheep before it was successful?
July 1996
227 attempts
