Artificial Selection And Domestication Flashcards
Domestification definition
Breeding under human control
Provides a product or service useful to man
Tame
Has been selected away from the wild type
What is a domesticated animal
The result of the domestication process
Breed definition
A group of animals that has been selected by man to possess a uniform appearance that is heritable and distinguishes it from other groups of animals within the same species
Taming definition
The behavioural manipulation of a wild animal to allow it to be confident around humans
Pet definition
A domesticated species kept by humans for aesthetic reasons or for pleasure
Feral definition
A domesticated species that has reverted to living in a semi-natural state
How is domestication studied
Archaeology- bones
Archeological and historical records of human civilisation
Genetic evidence
Phylogenetic analysis
Why did domestication take place
Climate change forced a more sedentary lifestyle
Settlement size of populations meant hunter-gathering was no longer a viable source of food
Animal partners
species that have been completely moulded by humans and have changed their physical and behavioral characteristics in response to artificial selection by humans
Have undergone complete domestication from a Progenitor species
Have undergone selective breeding to develop distinct breeds
What characterises animal partners
Being represented by numerous breeds, each selectively bred for certain characteristics that are enhanced to increase their value to human society
Exploited captive mammals
Have been enfolded into human society
Have not experienced a lot of selective breeding- so are very similar morphologically to their ancestral species
Key centres for domestication
Central and South America
South-western Asia
Far east Asia
Small mammals
Include fur-bearing species or those providing a product or service
Classification of domesticated mammals
Animal partners
Exploited captive mammals
Small mammals
Experimental domestications and game farming of mammals
Husbanded birds
Equivalent to animal partners- selected and modified into breeds
Eg pigeons or song birds
Ranched and game birds
Equivalent to exploited captives
Galliforms
Fowl
Turkey
Guinea fowl
Partridges
Pheasant
Quail
Anseriformes
Goose
Chinese goose
Muscovy duck
Mallard
Ratites
Ostrich
Emu
Rhea
Ratites
Ostrich
Emu
Rhea
Progenitor species
The ancestor of the animal partner
Biological process of domestication
Founder group becomes habituated to humans
Changed with successive generations by natural selection- those able to survive in the man-made environment survive and breed
Changed by artificial selection of traits valued by humans for economic, cultural or aesthetic reasons
Conditions that predispose animals to domestication
1 – animals should be “hardy”: must be able to survive removal from its mother before weaning and to adapt to a new diet and environment.
2 - behavioural structure of the species should be allied to that of humans: normal behaviour pattern based on a dominance hierarchy (can accept a human leader)
3 – species should be “comfort-loving”: not adapted to instant flight when threatened.
4 – fast rate of growth.
5 – animals should be “useful”: provide food in an easily accessible form.
6 – breed freely in captivity.
7 – easy to control: placid, versatile in feeding habits and gregarious so that a herd or flock sticks together
Home range definition
A restricted area within which individual groups of animals live
Usually the area around a home site over t which the animals search for food
Home range definition
A restricted area within which individual groups of animals live
Usually the area around a home site over t which the animals search for food
Territory
An area defended from others of the same species
Usually by males
Domestication of sheep/goats vs gazelle/deer
Sheep and goats have a social system based around a single dominant leader and have a home range
Gazelle and deer are territorial animals that live in herds without any social structure based on dominance hierarchies
So sheep and goats more easily kept in captive conditions as social leader replaced with a human
General effects of domestication
Reduction in body size
Changes in body proportions and appearance
Internal characters and dentition
Neoteny
Behavioural changes
Castration
Body characteristics in domesticated animals
Dwarf and giant varieties
Piebald coat colour
Wavy or curly hair
Rolled tails
Floppy ears
Shortened tails- fewer vertebrae
Changes in reproductive cycles (all species except sheep)
Why does domestication cause a reduction in body size
Poor nutrition limiting growth
Selection for smaller, more manageable animals
Changes in appearance and body proportions due to domestication
Variation in colouration
Thickness of wool coats
Self-shedding wool has been bred out of modern sheep
Changes in internal characters as a result of domestication
switch from storage of fat around the visceral organs to subcutaneous locations and as bands within muscles.
—-Fat may be less desirable now from a nutritional perspective but in early societies it was valued as a key food stuff and so there was selection for increased fat deposition
Decrease in brain size
Neoteny
Retention of juvenile characteristics in sexually mature adult animals
Why are neotenous changes advantageous in domestication
Ensures dominance over domesticated animals due to juvenile behaviour
Why is castration important in domestication
Bones grow in length rather than girth
More fat laid down in body tissues
Placating effect on make animals- useful for potentially aggressive species
Importance of livestock breeds
Historical value fuels interest in old breeds
Breed differentiation provides genetic variability within the population of any species as a whole.
Loss of any breed type leads to a reduction in the genetic pool.
Maintenance of ancient breed types is critical to ensure that relatively unselected animals, genetically relatively close to the wild progenitor, are available for modern breeding programmes
Conditions that favour human population growth also favour breed diversification
Breed diversification is more likely in remote or difficult areas of the globe
Mutation
A sudden heritable change in the genetic material (duplication, replacement or deletion of a gene)
Cline
A gradation of measurable characters that are unidirectional and pass into each other without discrete breaks in sequence
- non-discreet mutation produces a subtle change and due to interbreeding a cline is produced
Inbreeding
Mating of individuals more closely related than average pairs in the population
Process of breed differentiation - biological
1:- A type of animal is defined that is more useful and desirable than the ordinary type but it is not differentiated in pedigree. This distinction may reflect recognition of a cline or the development of a mutation
2:- Some of the best animals of that type are gathered into one or a few herds, which then cease to introduce much outside blood. This population then undergoes inbreeding so that the animals become distinct from other animals in other captive populations.
Process of breed differentiation - biological
1:- A type of animal is defined that is more useful and desirable than the ordinary type but it is not differentiated in pedigree. This distinction may reflect recognition of a cline or the development of a mutation
2:- Some of the best animals of that type are gathered into one or a few herds, which then cease to introduce much outside blood. This population then undergoes inbreeding so that the animals become distinct from other animals in other captive populations.
Types of variability
Discrete mutations
Clines
Types of variability
Discrete mutations
Clines
Process of breed differentiation- sociological
3:- If this process is successful then the breed becomes more popular and more herds are established from the original inbred population. Marketing of the breed is crucial in getting accepted and expanding its numbers.
4:- Once the breed becomes numerous, a herdbook is established to record the numerous pedigrees.
5:- A breed society is formed to safeguard the breed and to advance the interest of the breeders.
What did domesticated cattle descend from
Aurochs
Where did wild aurochs originally survive
1300- NE Europe
3 main types of British cattle
Beef
Dairy
Dual-purpose
Why are beef cattle chose
Yield
Hardiness
Rate of maturing
Eg Lincoln red, Aberdeen angus
Why are dairy cattle chosen
Buttermilk content
Yield
Eg Ayrshire
, jersey
Why are dual purpose cattle chosen
Yield of milk and meat
Location
Eg south Devon, belted Galloway
Progenitor species of guinea pigs
Cavia aperea
Cavia tschudii
Progenitor species of domestic cat
African wild cat- Felis sylvestris
Self-domesticated cats
Cats probably ‘self-domesticated’ because they were attracted to human habitation by rodent pest of food stores. Killing mice and rats would have endeared cats to early humans.
