Bio evolution and speciation key definitions

Homo Habilis tools

Oldowan tools are stone tools that have had flakes struck off one side of a pebble

Homo Erectus

Acheulean tools are stone tools that have had flakes struck off two sides

Neanderthal tools

Mousterian tools are stone tools that have been made from large flakes using levallois method

Homo Sapien tools

Upper paleolithic very wide variety and finer like blades and hooks

Skull trends exocranial

• Changes in diet bring about change in teeth, sagittal crest

• Diminished brow ridge possible as less stresses during chewing

• Decreased zygomatic arch, as the selection pressure of having the muscles for chewing are lessening

• Decreased prognathism/ muzzle-like

Skull trends endocranial

• Increased frontal lobe selected for with increased expression, memory, judgement, which could have made communication clearer and hunts and relationships more successful

• Increased cranial capacity

• Broca’s area for speech production

• Wernicke’s area for comprehension

Pelvis adaptions

Pelvis became more bowl shaped with a larger surface area. The advantage of this is more attachment site for walking muscles (gluteus) and also support for torso when upright walking. As there was now more distance walking expected with the habitat change to less vegetation, this would aid in the success of this

Feet adaptions

Big toe moved more in line. This would benefit thrust when walking, less energy in walking. Arch become more defined offering more support when walking

Arm:leg adaptions

Legs grew to be longer than arms which is more efficient for bipedal locomotion as most of the energy is used from the legs, quadruped have longer arms to legs which is efficient for arboreal living

Foramen magnum adaptions

Foramen magnum became more centralised which balances the head without the need for muscles in bipedal walking

Valgus angle adaptions

Valgus angle of the femur increased offering more support and less sway when walking bipedally which is more energy efficient

Spine adaptions

Changes in the spine shape to more of an s shaped spine with curvature enables support from the stresses to the body in bipedal walking. It is also a pillar for more even weight distribution bringing the upper torso over the hips allowing for more balance and acting as a shock absorber

Changes in hands

• Fingers get shorter/ thumb gets relatively longer

• First metacarpal is connected to the wrist by a saddle joint

• Finger bones are straighter

• These changes allow for the precision grip (ability to perform fine manipulative movements) and the power grip (ability to have a clamp like formation in which the fingers and the palm are partly flexed and pressure is applied by the thumb)

Domestication settlements benefits and costs

• Benefit of animal / plant, regular food supply

• Benefit of animal / plant, animals can be bred and eaten so less energy used than hunting

• Benefit of a settlement, less energy needed to keep looking for shelter

• Benefit of a settlement, people can begin to specialise in their jobs

• Cost of a settlement, less room between people so more diseases and chance of conflict

• Cost of a settlement, food may be less varied due to less hunter gathering

• Health is affected by disease and famine

Out of Africa theory

Homo Erectus left Africa then later Homo Sapiens

Multiregional theory

Homo Erectus left Africa and dispersed, regional populations slowly evolved into modern humans

Biological evolution

Occurs through genetic change and involves the transfer of DNA from one generation to the next

Cultural evolution

Transmission of knowledge from generation to generation, not passed on by genetics but by learning

Use of DNA, mtDNA, Y chromosome in human ancestry

• Mitochondria are inherited from the mother only (mtDNA) or Y chromosome from father only

• Mitochondria/ Y chromosome is used as a molecular clock, to work out time from divergence/ no recombination

• Nuclear DNA can be sequenced to look for genes, increased genetic variation indicate greater time since divergence

Multiregional model

• Homo Erectus left Africa and dispersed around the world where regional populations slowly evolved into modern humans

• Some level of gene flow between geographically separated populations prevented speciation, after the dispersal

• All living humans derive from the species Homo Erectus that left Africa nearly 2 million years ago

• Natural selection in regional populations, ever since their original dispersal is responsible for regional variants we see today

• Emergence of Homo Sapiens was not restricted to any one area but was a phenomenon that occurred throughout the entire geographic range where humans lived

Out of Africa model

• Modern humans evolved relatively recently in Africa, migrated into Eurasia and replaced all populations that had descended from Homo Erectus

• After Homo Erectus migrated out of Africa the different populations became reproductively isolated, evolving independently, and in some cases like Neanderthals, into separate species

• Homo Sapiens arose in one place (Africa)

• Homo Sapiens migrated out of Africa and replaced all other human populations without interbreeding

Species

Organisms that can reproduce to produce fertile offspring

Speciation

Process by which new species are formed from ancestral ones

Allopatric speciation

When populations become geographically isolated, each are subjected to different selective pressures and reach a point where they are reproductively isolated and no interbreeding can occur if they were to come across each other

Sympatric speciation

When populations form a new species within the same geographical area as the parent species

Adaptive radiation

The rapid formation of new species from a common ancestor

Genetic drift

Random fluctuations in the frequencies of alleles from generation to generation due to chance events, much more evident in small populations

Gene flow

When individuals move between populations, and this allows new mutation / new combinations of alleles to move into each population, so the species does not diverge

Natural selection

When inheritable traits that make an individual more likely to survive long enough in its environment to reproduce, become more common in the population over successive generations

Mutations

Source of all new alleles can bring about new traits. Natural selection selects for favourable phenotypes thus selecting for mutation / genotypes. Some individuals have more reproductive success than others and leave more viable offspring over their lifetime

Polyploidy

Results from hybridisation between species. This occurs when chromosomes do not separate properly and so gametes have a diploid number of chromosomes

Convergent evolution

Similar features arising in non related species

Divergent evolution

Where two or more species form from a common ancestor

Coevolution

Two species that act as selection pressures on the evolution of each other

Analogous structures

Structures with very different evolutionary origins that appear very similar because they carry out the same or very similar functions

Homologous structures

Similar structures in different species that have the same ancestor

Pre-zygotic RIMS

• Temporal, behavioural, ecological, geographical, structural, mechanical

• They may be due to mutation resulting in different timing of mating, different courtship displays, different feeding patterns, preference for a different location or a change to the species phenotype

Post-zygotic RIMS

Barriers that occur after zygote formation such as organisms that die as embryos or those that are born sterile

Gradualism

A gradual change due to the selection pressures remaining constant, as even though mutations still randomly occur, no major change in form is selected for

Punctuated equilibrium

Long periods of stasis of the same form being selected for and interrupting this, we see suddenly new forms / species that would have resulted from diverse selection pressures selecting rapidly for a change in form. Thus, mutations that offered a different trait are selected for

How can populations become different

• Natural selection

• Mutations

• No gene flow

• Non random mating

• Genetic drift

Ring species

A series of geographically neighbouring populations that are closely related

Cline

A gradual variation in the physical characteristics of a species or population over its geographical range

Gradualism

Environmental conditions change very slowly after populations are separated perhaps due to selection pressures not being very intense, any change in allele frequency will occur over a long period of time resulting in the gradual change of the species 

Founder effect

When a new population is established by a very small number of individuals that have become reproductively isolated from a larger population

Bottleneck effect

A random effect that drastically reduces the size of a population and decreases the gene pool as many alleles are lost

Gene pool

Refers to the total number of genes of every individual in a population

Mitochondrial DNA (mtDNA)

An important tool for tracing evolutionary relationships within a species it is inherited from maternal lineage, it is direct and has no recombination maintaining sequence fidelity

Population

Members of a species that live in the same geographical area and they share a common gene pool

Allele frequencies

The number of times that an allele occurs in a population

Niche

Encompasses both the physical and environmental conditions an organism requires and the interactions it has with other species