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Flashcards in Human Evolution - biological evolution Deck (18):

Describe biological evolution

Biological evolution is the evolution of genetic information from parent to offspring. Happens over a long period of time


What is a trend

A pattern of gradual change in evolution


What is the difference between quadrupeds and bipedal locomotion and bone structure? Describe the pelvis and bones

Quadrapeds have a long and narrow pelvis as they knuckle walk, with the femur going straight down. Bipedals have a forwards facing pelvis and have a short, broad pelvis with a bowl like structure


Who was the first species to walk bipedally?

Australopithecus afansis was the first species, known as Lucy.


What is the difference between the pelvis shape in quadrapeds to bipedals?

What are the advantages for the bipedals pelvis?

The bipedal pelvis is short and wide and the quadrapeds is long and narrow.

The bowl shape accommodates the muscles associated with bipedilsm such as the gluteus maximums. The femoral attachement is angled which creates the valgus angle and the spine and internal organs are placed over the centre of gravity.


What is the valgus angle?

The angle the femur (thigh bone) makes in relation to the knee


What's the difference in the feet of a bipedal and a quadraped? What are their adaptive advantages?

Give two examples.

Quadrapeds have a diverging toe for climbing trees. Bipedals have elongated, in line toes which aid in the forward thrust movement and balance.

Hominin feet have an arch to act as a spring to reduce shock. Quadrapeds have a flat foot as they are arboreal habitually.


Why did hominids develop a reduced prognathism?

The prognathism was reduced because of the change in early hominin diets. Early hominins started eating softer foods (meat) meaning our large jaws for eating fiborous plant matter was lost. This happened after bipedalism as free hands was needed to make tools and hunt for prey.


What is the function of the sagitial crest and brow ridges?

To support the large muscles that were required for eating a herbivorous diet (fibourous plant matter)


What species has an exception of the large brow ridges?

Homo Erectus


What is the change in the skull due to bipedalism?

The position of the foreman magnum - quadrupeds have them at the rear, bipedals have them in the centre


What is the adaptive advantage of having a S shaped spine? Give two points

Absorbs shock from bipedal movement and ensures the centre of gravity is located just above the pelvis


What changes occurred from being a quadruped to a bipedals chest? Describe one effect of this

The chest changed from being large and wide in quadruped to being closer to the spine in a bipedal.

This is because in a bipedal, the centre of gravity is in the pelvis so having the chest closer to the spine ensures the centre of gravity stays at the top of the pelvis.


What are postitives and negatives of being bipedal?

Being bipedal saved energy for walking upright, this was an adaptive advantage when bushlands changed into a savanah 6 million years ago. It also meant they could see over the grasslands for predators, however it also meant prey could spot them better.

Standing upright meant 60% less surface area is exposed to the sun, meaning thermoregulating was able to be achieved easier.

This is a benefit as it meant more early hominins were able to reach maturity and pass on their genes


Why is being bipedal an adaptive advantage for thermoregulation? Give two points

Being taller meant there was better air flow, there for thermoregulating could be achieved by being further away from the ground. Also being bipedal there is 60% less surface area facing the sun compared to a quadruped


What are the hands of apes and quadrupedal adapted to doing and how does this affect their adaptation of hands?

Quadrupeds are adapted to being habitually on all four limbs meaning the hands are adapted to supporting locomotion rather than manipulation of objects.


Why have human hands got an opposable thumb and have more precision?

Because human hands aren't used in locomotion, instead they are used for the manipulation of objects. Therefore, the human hand has adapted to have more precision


What is the joint called that the thumb is joined to the wrist by that allows the thumb to cross the palm and touch other fingers?

The saddle joint