Bears Flashcards
Obligate Carnivore
Definition
animals that depend soley on animal flesh for nutrient requirements
Facultative Carnivore
Definition
animal that depends on animal flesh for its nutrient requirements but also consumes non-animal food
Omnivore
Definition
animal that eats both animal and non-animal food
Apex Predator
Definition
at the top of the food chain
Homoplasy
Definition
a characteristic shared by a set of species that is not present in their common acestor
Extinct Bear Species
Arctotherium angustidens
- largest bear ever found
- south American
- alive 2.5mya - 11kya
- 3500Ibs / 250 stone
Extinct Bear Species
Ursus spelaeus
- the cave bear
- UK & Ireland
- lived in caves only leaving to find food
- especially limestone caves
Extinct Bear Species
Arctocus simus
-giant short faced bear
Extinct Bear Species
Ursus maritimus tyrannus
- King Polar Bear
- UK and Northern Europe
- c. 130kya
Extinct Bear Species
Agriotherium africanum
-bear with the strongest bite
What has been the general trend in bear size over time?
they have become smaller
Modern European Carnivores
- wolves
- lynx
- wolverine
- eurasion brown bear
What is comparative genomics used to understand?
- population movement
- relationships between species (extant and extinct)
- when a species diverged / emerged
- what DNA changes or adaptations are unique to a species
- what makes a species unique
Modern Bear Species
Sun Bear Panda Sloth Bear Spectacled Bear Asiatic Black Bear American Black Bear Brown / Grizzly Bear Polar Bear
What are the closet non-bear relatives of extant bears?
racoon
lesser / red panda
Change in the Range of the Grizzly Bear Over Time
post-glacial - most of north America
historic - north and west America
modern - far north America, beginning to overlap with the range of the polar bear
Polar Bear
- diet is predominantly lipids and fats
- tend to have twins or triplets as they release 2 eggs at a time
- their milk is 27% fat
- 50% body fat is healthy for an adult polar bear
- diet is based on large quantities of seal fat
- most carnivorous member of the bear family
- they metabolise fat to get water so don’t need to drink
Which bear is the closest relative of the polar bear?
the Grizzly bear
Brown / Grizzly Bears
- omnivores
- long claws for digging
- adapted to survive the changing seasons
- have different diet in different seasons
- may eat up to 40kg of food per day
- can increase body weight by 1kg in a day
- eat fruit, berries and nuts
Tetrapod
Definition
has 4 limbs
Homolog
Definition
a feature common to all descendants of a most recent common ancestor
Homology
Definition
the existence of shared ancestry between a set/pair of structures/genes in different species e.g. fore limbs
Alignment
Definition
positional homolog
Mutation as a Molecular Clock
- it is possible to count the number of mutations on a particular gene
- in the alpha haemoglobin gene (NOT ALL GENES) the number of base substitutions is proportional to time as judged by the fossil record
Genetic Diversity and Effective Population Size
- genetic diversity is a function of effective population size
- in a small population genetic diversity is relatively low
- in a larger population genetic diversity is much greater
Genetic Diversity
Brown Bears and Polar Bears
Polar Bears - 2.6 million unique mutations
Brown Bears - 7.7 million
Showing that polar bears have a much smaller effective population size than brown bears
Reconstructing Ancestral Brow & Polar Bear Population Size
900kya - 123k big drop 500kya - 20k TODAY Polar - 68k Brown - 463k
When did Polar bears and Brown bears diverge?
- molecular evidence - 470kya
- fossil record - 479-343kya
- mitochondrial DNA - 450kya
Hybridisation - Polar and Brown Bears
- at least 4 intragressive events
- polar bears moved south and brown bears moved north
- polar and brown bears interbred producing viable fertile offspring
- these hybrid bears then interbred with both the polar bear and brown bear populations
- then they separated north and south again
- interbred separately for thousands of years
- this means that the evolutionary history of brown bears and polar bears is interwoven and complex
How did Polar bears adapt?
- adipose tissue development
- heart development
- blood coagulation
- homeostasis - regulation of body fluids
- sarcomere organisation
- white fur colouration
- fatty acid metabolism
- all adapted in a relatively short period of time
Neutral Selection
Definition
non-advantageous, random genetic drift occurring
Purifying Selection
Definition
pressure to retain the current genotype
Positive Selection / Adaptive Evolution
pressure for change of the genotype to increase fitness
