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LEC 141 - Evolutionary Biology > Week 2 > Flashcards

Week 2 Flashcards

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1
Q

Established around 80 MYA

A

Primate ancestors: ‘super order’ of Euarchonta

50 MYA split into prosimians and simians

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2
Q

Prosimians

A

Grasping fingers and toes
Binocular vision
Mostly nocturnal
Mostly arboreal

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3
Q

First Simians

A

First: direct ancestors of monkeys and hominids, originated in Africa or Asia (old world) (new world in South America)
Different adaptive radiations over 40 MYA, did new world reach South America via rafting?

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4
Q

Simians

A

Overlapping fields of vision
Opposable thumbs (not all genera)
Live in groups (social)
Mostly diurnal

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5
Q

Humans vs Chimps

A

Study in 2005 compared genomes:
- 96% similarity overall
- 99% similarity in coding DNA

  • number of genetic differences is only 10x greater than number of genetic difference between 2 humans
  • very similar genetics, but difference in how these are expressed
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6
Q

Key ape characteristics

A
  • larger brain relative to their body size (compared to other primates)
  • flexible behaviour (due to behavioural adaptations for example)
  • tail-less
  • some highly social
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7
Q

Chimps vs Hominina anatomy

A

Chimps:
- skull attached posteriorly
- spine slightly curved
- arms longer than legs and also used for walking
- long, narrow pelvis
- femur angled out

Hominina:
- skull attached inferiorly
- spine s-shaped (shock absorption, stand upright)
- arms shorter than legs and not used for walking
- bowl-shaped pelvis
- femur angled in

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8
Q

Aridipithecus ramidus

A key step towards human evolution?

A

Dated 4.4MYA
Chimp-sized brain
Broader diet than modern chimps
At least partly bipedal (use it two legs for walking)
Recent discovery

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9
Q

Australopithecus

Close relation to Homo sapiens

A

Round jaw
Brain size 35% of modern humans
Sticky build
Large teeth and jaws
Various ways of moving, but walk upright

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10
Q

Skull shape change over time

A

Flat face
Brown ridge bone size
Steepness of skull moving forward
Etc

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11
Q

Lucy

Australopithecus afarensis
(May be a direct ancestor of genus Homo)

A

Found in Ethiopia (1973)
3.2 MYA
Skeleton 40% complete
Human-like teeth
Ape-like head

Knew she was a female due to height (usually females in species were smaller than males), and pelvis size

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12
Q

Homo habilis

A

Appearance: 2.5MYA
Found with many stone tools
Short stature
Disproportionately long arms
But larger brain than Australopithecines - 50% of current human brain size
Shorter jaw

Behavioural adaptations? - tool useage

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13
Q

Homo erectus

A

Replaced Homo habilis
2 MYA
About 5 feet tall
Long straight legs for walking (can move to other habitats - enables further evolution)
Thick skull with steep forehead
Larger brain (similar to modern human)
But still prominent brow ridge
Rounded jaw (ability to talk?)
Social development: cave dwellers/wooden shelters, built fires, social groups, tool use

Originated in Africa - was it the first to leave?

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14
Q

Homo neanderthalensis (Neanderthal man)

A

Appeared 600,000 years ago in Europe and W/C Asia
12-14cm shorter than modern human
Large skulls, heavy bony ridges over brows
Bugger brains than modern human

Made diverse tools
Lived in huts and caves
Took care of injured (emotional development)
Buried dead (symbolic thinking)

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15
Q

Cro-Magnon Man

Homo sapiens sapiens
(Subspecies)

A

Replaced Neanderthals by 30,000 years ago, but may have evolved 200,000 years ago (overlap in time)

Facial expressions
Complex social organisation
Sophisticated tools
Language
Loss of body hair (pigmentation)
Cave painting
Move and run over greater distances
Successful hunters

Colonised plains, making marks on landscape (start of colonisation and distribution of humans)
(Stated global distribution: spread across Siberia and North America by 13,000 years ago)

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16
Q

Which organisms form the great apes?

A

Hylobatidae
Pongo (orangatan)
Gorilla
Pan (chimp)
Homo

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17
Q

Origin of modern humans: Out-Of-Africa

A

Suggests Anatomical Human evolved within Africa 200-100KA and then left to colonise new continents

They ‘replaced’ descendants of Homo erectus in regions outside of Africa.

If this hypothesis is correct, global populations should be more closely related than if the multi-regional hypothesis was true

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18
Q

Origin of modern humans: Multiregional hypothesis

A

Focused on age of most recent hominid ancestor from fossil record (last common ancestor in Africa 1.5MYA)

Homo erectus left Africa first and colonised new continents (scattered throughout Europe and Asia). Then Anatomical Human evolved outside of Africa in multiple different regions

If correct, global populations should be more distantly related

Similarities of modern people are the product of occasional interbreeding between neighbouring populations - differences result from groups of people evolving in discrete environments (giving rise to different phenotypes)

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19
Q

Out of Africa vs Multiregional

A

Homo sapiens evolved from each region of local populations of H. erectus 1-2 MYA
H. sapiens less closely related

Homo sapiens evolved from second major migration out of Africa ca. 100KA
H. sapiens more closely related

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20
Q

Evidence for Multiregional hypothesis

A

Study in Nature unveiled Hominina fossils dated 1.2-1.1 MYA in Spain

Supports ‘earlier’ migration out of Africa = Multiregional hypothesis

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21
Q

Evidence for human evolution: molecular genetics

A

Mitochondrial DNA; slow changing/consistent

Phylogenetic tree shows evolutionary relationships indicating origions of anatomical human (AMH) in Africa

Dated time of genetic divergence at 200,000 years ago (Date is in between Multiregional and out-of-Africa hypothesis) - doesn’t support either model

Suggests single woman still in Africa from which all put mitochondrial DNA originates (Mitochondrial Eve - left Africa 160 KA?)

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22
Q

Evidence for human evolution: y-chromosome

A

Study comparisons from various geographic regions

Y chromosome used as has little crossing over during meiosis - diversity is limited to mutations

Can act as a marker for examining ancestry

Study shows divergence from one common male African ancestor 60KA

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23
Q

Evidence for human evolution: Neanderthals

A

They ‘split’ from descendants of African Homo migrants, but then extinct about 30KA

Some question if there is a missing link between H. erectus and H. sapiens

They coexisted with AMHs for at least 1000years

mtDNA typing shows sharp differences between AMHs and Neanderthals (= distinct evolutionary lines)

This favours out-of-africa model

24
Q

Origins of modern humans: Assimilation Model

A

Important contribution of a recent common ancestor from Africa (out of Africa model) but emphasised assimilation rather than replacement, as they colonised the rest of the world

Predicted that archaic people (eg Neanderthals) contributed about 10% of living peoples genome

Received little attention until recently

25
Q

Recent evidence Assimilation Model

A

Sequenced complete Neanderthal genome

  • shows 1-4% similarity with the DNA of Europeans and Asians
  • but not in African populations

Suggests both models perhaps work alongside eachother, some left Africa and then evolved while others evolved in Africa and then left while some never left or even returned back to Africa

26
Q

Origins of modern human: Leaky Replacement Model

A

Neanderthals and Denisovan populations split about 200,000 years ago - share some DNA

When modern human left Africa, interbred with Neanderthals about 100,000 years ago, these evolved into modern day Asians and Europeans

A subset of these went east and interbred with Denisovans - forming the basis of modern-day Melanesians (Path of New Guinea)

Interbreeding still limited - however, Neanderthal x Denisovan hybrid remains were recently found

27
Q

Key phases of human evolution coincide with flickers in eastern Africa’s climate (environmental impacts)

A

Lake sediment record identified phases of climatic stress / favourable conditions

Anatomically diverse hominin groups inhabited area during stable phase

Extreme phases such as extinctions can also change evolutionary pathways

275-60 KA environmental shifts occurred: technologies changed, emergence of H sapiens in Eastern Africa

60-10 KA - extreme environmental fluctuations: alignment of humid E Africa with wet NE Africa and Mediterranean favourable migration routes = global dispersal (able to move between continents easier, impacting evolution and diversity)

28
Q

What distinguishes us from chimps?

A

Bipedalism / anatomical

Permanent bisexual social groups

Large brain: 1400 cc.

Capable of complex learning

Advanced use of language

Social and cultural development

Food obtained through division of labour and shared efforts

29
Q

Homo Similarities with other primates

A

Reproductive strategies (classified into K and R (we are K))

Enhanced communication / social behaviour (some apes use sign language and only mix to mate while we have complex social structures and we use complex array of different sounds (it’s suggested we started off clicking - can still be seen in some African language)

Tool use

30
Q

Why did human language develop?

A

Possible scenarios:
Substitute for grooming (was a way to communicate)
Hunting theories
Language as a way of thinking
Motherese
Took-making
As a warning

Theories for how it started to develop are on PowerPoint Lecture 5 LEC 141

31
Q

How does agriculture influence human evolution

A

Start of Holocene (11.6 KA), cultivation started of cereal grains

Move away from hunter-gatherer, now live in social groups & establish crops

Development of agricultural centres eg SW Asia, C&S America, SE Asia

Domestication if livestock food courses (9 KA) and also physical work

Commencement of global anthropological impacts

32
Q

Drivers of human evolution

A

Fluctuating environments = changing food sources and environmental conditions

Early Hominina we’re vulnerable to predation
- fire as protection, communication to warn, building shelters, tools as weapons, etc

Adaptability

33
Q

Related theories of evolution: Lamarckism

A

‘Heritability if acquired characteristics’ or instruction by the environment rather than selection by it eg ostrich callus and giraffes necks

Epigenetics provide a heritable mechanism (Darwinian mechanism for Lamarckism evolution)

34
Q

What are the various theories on the origin of modern humans?

A

Out-of-Africa

Multiregional hypothesis

Assimilation

Leaky replacement

Others

35
Q

What is macro evolution

A

Evolutionary change over long periods of time of a large scale

For example: origin of new taxonomic groups, mass extinctions and evolutionary trends

36
Q

what is Micro evolution

A

It is the basis of natural selection, where a population progressively adapts to its environment

It’s change at/below species level for example within a species,

Example: natural selection. Individuals with heritable advantageous characteristics produce more successful offspring than those without

37
Q

What is a population

A

A group of individuals of the same species living in a particular geographical location

38
Q

Define genotypes

A

Genetic makeup of an individual

39
Q

Define phenotype

A

Observable characistics
(Depends upon organisms genotype and on its environment)

40
Q

Define chromosome

A

Gene carrying structures found in nucleus

41
Q

Homologous chromosome are

A

Chromosomes that carry genes controlling the same characteristics

42
Q

Define alleles

A

Alternative forms of a gene (variation in the DNA sequence for a given gene)

43
Q

What is homozygous chromosome

A

Homologous chromosomes containing the same allele

44
Q

Heterozygous chromosomes are

A

Homologous chromosomes that contain different alleles

45
Q

What is karyotyping

A

Pairing and ordering of chromosomes
Pseudocolours identify alleles
Chromosomes occur in pairs in the cell

46
Q

4 ways of asexual reproduction

A

Binary fission
Budding
Parthenogenesis
Vegetative reproduction and fragmentation

47
Q

What is binary fission

A

One cell divides into two cells of similar size
Both have same genetic material
Same size

48
Q

What is budding (asexual reproduction)

A

Mew individuals ‘split’ off form parent cell
Both have same genetic material
Bud cell smaller than parent cell

49
Q

What is parthenogenesis (asexual reproduction)

A

Development of unfertilised egg

No genetic input from males

Obligate in some species (only reproductive method)
Facultative in other species (choose to use this)

50
Q

Vegetative reproduction (asexual)

A

New individuals form without production of seeds or spores

New plant form out of rhizome or stolons / bulbs or tubers / shoots and suckers

51
Q

What is Fragmentation (asexual reproduction)

A

Organism splits into fragments

Continue to develop into complete organisms

52
Q

What process does sexual reproduction happen?

(More on sexual reproduction on Lecture 6 LEC 141)

A

By meiosis

Haploid genets formed - fuse to form a diploid zygote.

Individuals are genetically different from their parents as a result of 3 events: independent assortment, crossing over, random fertilisation

53
Q

What are 4 chromosomal mutations that can occur during sexual reproduction

A

Deletion
Duplication
Inversion
Reciprocal Translocation

54
Q

What is polyploidy

What 2 types are there?

A

Multiple sets of chromosomes

Occurs at cell / tissue / whole organism level
Common in angiosperms (flowering plants)
Liver cells are often polyploid

Autoployploidy
Allopolyploidy

55
Q

What is autopolyploidy

A

Error in meiosis/mitosis

Single species genome duplication (single parent)
Eg chromosome number increases from a diploid to a tetraploid (4 copies per cell)

56
Q

What is allopolyploidy

A

Error in meiosis/mitosis

Two different, related species interbreed, hybridise, then chromosome number doubles

Uncommon and usually sterile after

LEC 141 - Evolutionary Biology (4 decks)

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