Evolution and domestication of the horse, micro-evolutionary consequences, related species, inter-species hybrids.

Question 1

Taxonomy: Kingdom, Phylus, Class, Family, Genus

Answer 1

kingdom: animalia,
phylum: chordata,
class: mammalia,
order: Perissodactyla (non-ruminant, hooved animals)
Family: Equidae

Question 2

name x4 subgenus

Answer 2

Equus,
Asinus (equus asinus/ africanus) (domesticated ass),
Hemionus (asian semi-ass),
hippotigris (zebra).

Question 3

x4 different species of subgenus equus + latin name

Answer 3

Wild horses – Equus ferus Boddaert,
Prewalski horse/Taki – Equus ferus Prewalski,
Tarpan – Equus ferus ferus,
Domestic horse – Equus caballus.

Question 4

x5 interspecies hybridisation

Answer 4

Mule – Male donkey (jack) & female horse (mare). Usually sterile.

Hinny – Female donkey (jennet) & male horse (stallion). Less common. Also infertile.

zorse - female horse (mare) + male zebra (stallion)

zebra hinny: female zebra + male horse (stallion)

zebroid: female donkey (jennet) + male zebra (stallion)

Question 5

What is Haldane’s Rule

Answer 5

primarily the heterogametic sex (male) is affected by sterility in successful crossing of closely related species.

Question 6

x6 evolutionary forms of the horse (transitional species)

Answer 6

Evolution is well documented.
approx. 60 million year process.
Eohippus,
Mesohippus,
Mio-, mery-, pliohipps,
Equus.

Question 7

micro-evolutionary consequences:
x4 most important changes in modern horse

Answer 7

Size,
toe reduction (4 –> 1),
diet (omnivores -> herbivores),
teeth,
forest –> pasture

Question 8

where and when did domestication take place?

Answer 8

Occurred ~5000-6000 years ago.
1st – Central Asia,
later in Persia,
Egypt & Europe (3000-4000BC).

Question 9

what is the main ancestor of the modern horse?

Answer 9

Based on mitochondrial examination, Tarpan/Tarpan subspecies is main ancestor.

Question 10

what is the ‘wild’ horse?

Answer 10

Przewalkski horse is only remaining wild spp

Question 11

what are feral horses?

Answer 11

Have domestic ancestors but were born & live in wild
(‘dedomesticated’) -> Mustangs, Bramby

Question 12

when did horses arrive back into america after extinciton?

Answer 12

after 1492 due to Spanish invaders

Question 13

name some historical uses of horses

Answer 13

hunting,
chariots,
carriage,
coach,
transport,
military,
agricultural,
leisure.

Question 14

ancestors of the modern horse

Answer 14

tarpan (extinct),
west european forest horse,
przewalski,
mingolian taki,
mustang + bramby (returned to wild).

Question 15

micro-evolutionary consequences:
x10 consequences of domestication…
FMSBWDARCS

Answer 15

Fusion of chromosomes,
Mutations and selection,
Size variation,
Build + conformation,
Weight variation (50 - 1200kg),
Diet,
Accelerated ageing,
Reduced immune system,
Colour variations (bay, grey, dun, chestnut, palomino, buckskin).
Sexual activity.
forest –> pasture.

Question 16

Fusion of chromosomes: number of chromosomes in wild horses, asses, domestic horses, tarpan.

Answer 16

wild + domestic horses - 66 - > 64 presumption only,
ass - 62,
tarpan - unknown.

Question 17

mutations and selection: how many breeds are there?

Answer 17

much more diversity.
200+ breeds, breed groups and types.
many new mutations + harmful genetic diseases e.g. HWSD.
there is a high allelic polymorphism on the same gene locus across breeds.

Question 18

what type of size variations may occur?

Answer 18

size has increased immensely.
height is taken at withers.
under 148cm - pony.
over 148cm = horse.
dwarfism: falabella + shetland pony.

Question 19

mention build and conformation differences due to breeding

Answer 19

draft horses (heavy).
light horses.
certain breed characteristics - roman nosed + dish-faced.

Question 20

what is the effect of domestication on diet?

Answer 20

less effective feed conversion.

Question 21

what is the effect of domestication on immunity?

Answer 21

reduced immunity.
increased sensitivity to certain diseases e.g. respiratory diseases.

Question 22

what is the effect of domestication on sexual activity? (x3)

Answer 22

poorly expressed sexual dimorphism.
reduced fertility in some breeds.
was monoestrus, now seasonally polyoestrus.