bio what to know for SAC

Question 1

what are environmental selection pressures?

Answer 1

A factor in the environment that impacts an organisms ability to survive and reproduce
○ Limited resources
○ Deforestation
○ Changing temperature
○ Predation

Question 2

what is genetic drift

Answer 2

• Mechanism of evolution in which allele frequency of a population changes due to chance/random events
  ○ Affects the overall diversity of a population
  ○ More likely to be observed in smaller populations
  ○ More likely to see extinction in smaller populations

Question 3

why does genetic drift impact smaller populations more extremely?

Answer 3

smaller populations have less genetic variability so they are less likely to have the phenotypes that help them survive because they are vulnerable to new selection pressures and harmful alleles (genetic disease) due to inbreeding

Question 4

what is the bottleneck effect?

Answer 4

○ The size of the population is severely reduced and so the genetic diversity is reduced due to a chance event
§ e.g. natural disasters (floods, drought, earthquakes), famine, disease, oil spills

Question 5

what is the founder effect?

Answer 5

○ Reduction in genetic diversity/variation that occurs when a population is derived from a small group of the original population
§ May occur when small groups migrate or become isolated from the original population
§ Smaller population size = less genetic diversity
Often seen in the populations of islands which are colonised by individuals from mainland populations

Question 6

what is speciation?

Answer 6

The process of forming a new species separate from an existing one
- Slow and gradual process

Question 7

what is allopatric speciation?

Answer 7

○ Formation of a new species as a result of geographical barrier separating a population
i. Geographical barrier separates a population, preventing gene flow
ii. Different selection pressures act upon each population, favouring different phenotypes and allowing for genetic differences to accumulate
iii. Eventually, sufficient genetic differences accumulate so the two populations can no longer interbreed and produce viable and fertile offspring

Question 8

what is sympatric speciation?

Answer 8

○ Formation of a new species in populations located in the same geographical region and emerge as a result of different selection pressures acting upon different phenotypes within a population, causing individuals with certain phenotypes tro diverge from others and form a new species
§ Occur as a result of genetic abnormalities that occur during gamete formation, producing polyploid variants
□ Errors in mitosis could also cause offspring to have double the chromosomes that will change the phenotypes and over time allow for breeding isolation
§ EXAMPLE: Howea Palms
□ H. belmoreana is found in acidic/neutral pH soil
□ H. forsteriana is found in alkaline (high pH) soil called calcarenite.
Early studies suggest that this divergence was driven by soil pH impacting timing of flowering, forming a breeding isolation mechanism.

Question 9

what are the types of fossils?

Answer 9

body fossils
○ Preserved remains of an organism
e.g. freezing, petrification (fossilised forests), drying, permineralization

trace fossils
○ Indirect signs of life that give evidence of the organism’s presence
e.g. footprints, burrows, trails, coprolites (fossilised faeces)

Question 10

what are the categories of fossils?

Answer 10

Index fossils
○ A group of widespread fossils which existed for a short period and have a known age
§ Physically distinctive
§ Have had a large population
§ Have existed in many geographical areas
§ Only lived within a known short period of time

Transition fossils
○ Fossils that show traits that are common to both its ancestral group and its descendant group
Demonstrate the evolutionary changes between the two (ancestral + descendant)

Question 11

what is absolute dating and how is it used?

Answer 11

○ Used to date igneous rock (molten rock that has been solidified)
§ The igneous rock near the fossil is dated and hence the date of the fossil is inferred
○ When molten rock solidifies there are some radioactive isotopes of elements present
§ Over time, the radioactive isotopes decay to form the daughter element
Half-life: the time taken for half of the original radioactive isotope to decay

Question 12

what is relative dating and how is it used?

Answer 12

○ Uses the law of fossil succession to assign a fossil a relative age in relation to other fossils and rock strata (layers)
§ Law of fossil succession: sedimentary rock is formed by the accumulation of sedimentary layers on top of each other + the fossils closer to the surface must be young than those that are found below them
§ Scientists assign each separate stratum to a particular period of time
Does not determine the exact age of the fossil - just determines of this fossil is older or younger than another fossil

Question 13

what are conserved genes?

Answer 13

Genes that have remained largely unchanged throughout evolution and are found across the genome’s of many different species

Question 14

what are hominins?

Answer 14

• Humans are the only living hominins (TRIBE)
  
  • Bipedal (walk upright on two legs)
    ○ Bipedalism led to significant structural changes in hominins
    All hominins are hominids

Question 15

what are characteristics of hominins?

Answer 15

• smaller teeth
• parabolic dental arch
• foraum magnum is more centrally located
• no/small brow ridge
• no diastema

Question 16

hominin evolution: what are the trends of structural changes over time (general patterns)

Answer 16

spinal curve
- changed from ‘C’ shaped to ‘S’ shaped (curves in the upper and lower back)
- allows for weight to be supported vertically and allow for bipedalism

rib cage
- changed from funnel-shaped to barrel-shaped to help hominins remain upright and long periods of time

leg to arm ratio
- decreased as legs became more important for bipedalism (more useful for bipedal locomotion)

pelvis
- became shorter and more bowl-shaped to support the upper body while standing and walking upright
- in the Homo species, the leg attaches to the pelvis at an angle, allowing for them to walk upright more easily
- in previous hominins, their legs attached to the pelvis may be been in a straight angle, causing their legs to swing out wider (slower)

big toe
- became more protruded while the other toes became more aligned as they had less use for gripping

foot arch
- increased to accommodate for bipedal locomotion

heel size
- increased to increase the SA of the foot, making bipedal locomotion more efficient (more energy efficient + less impactful to the foot)

Question 17

Hominin evolution: what are some of the changes in diet and its evidence?

Answer 17

• Inferences can be made by their tooth structure
  ○ Small molars with thin enamel suggested a diet of fruit and soft leaves
  ○ Larger molars suggested a mixed diet of fibrous plant material
  
  • Inferences can be made by their skeletal structure
    § e.g. Australopithecus were herbivores (evident by enlarged rib cage to support a pot belly and larger digestive tract to digest plant materials)
    e.g. Homo erectus show changes in skeletal structure, inferring reduced digestive trace to support meat in their diet

Question 18

Hominin evolution: what are some of the cognitive changes?

Answer 18

• Increase in brain size can be seen across Homo skulls, indicating a selection pressure that benefitted the ability to problem-solve
  ○ Cerebrum became more folded (increased SA of the brain), enhancing cognitive ability
  § Increased folding allowed for speech, feeling complex emotions, high order decision making, greater self-control, abstract thinking and planning
  □ These cognitive changes allowed for greater emotional skills, hunting techniques, and communication which drives technological and cultural evolution
  Inclusion of meat in early Homo diets allowed for the brain to grow larger in order to avoid predators and hunt larger game

Question 19

what is the expensive brain hypothesis?

Answer 19

It tries to understand advanced cognitive ability in terms of advantages like predation reduction and improved food production compared to negative impacts such as increased energy requirements and higher childbirth complexity

Question 20

what is the Australopithecus Afarensis?

Answer 20

○ Existed about 4mya
○ Has features that indicate bipedalism but also possesses features normally associated with arboreal existence
§ Human-like pelvis and leg bones confirm bipedalism
○ Small, gracile, small-brained
○ Height of 1.0-1.5m (sexual dimorphism)
Skull similar to chimpanzees (flat nose, no chin, low forehead, bony brow ridge)

Question 21

what is the Homo Neanderthalensis?

Answer 21

○ Existed 400,000-40,000 years ago
○ Lived in cold climates
○ Used fire and fine tools, ornaments, clothing
○ Co-existed with H. sapiens and interbred
Capability for speech and possible language

Question 22

what is the Homo Florensiesis?

Answer 22

○ Existed 95,000-13,000 years ago
○ Found on the Indonesian island of Flores
§ Small stature may have resulted from long-term isolation (endemic dwarfing
§ Despite their small brain sizes, they used tools and fire, hunted dwarf elephants

Question 23

what are homo sapiens?

Answer 23

○ Appear to have evolved in Africa 200,000 years ago and migrated out of Africa 65,000 years ago
○ Now occupy most terrestrial environments
§ Referred to as the “Cro-Magnons”
□ Large brains (1350ml)
□ High, steep foreheads
□ Narrow skulls
□ Absent brow ridges
□ Small eye sockets
□ Pointed chins
No gap between the third molar and jawbone

Question 24

what are key cognitive behaviours associated with the Homo species?

Answer 24

• Making and using fires
  
  • Group activities
  • Use of tools and technology
  • Caring for the aged and sick
  • Burying deceased members
    Art, mathematics, language, symbols, and music