Grasses and Humans

Question 1

Monocots

Answer 1

-Have one cotyledon (embryonic leaf) within the seed
-Parallel veins
-Scattered vascular bundle in the stem
-3 fold symmetry (flowers)
-No secondary thickening
-Can have intercalary meristems

Question 2

What are cotyledons?

Answer 2

“Seed leaves” that are produced in the embryo which have a different structure to true leaves.

Question 3

Dicots

Answer 3

-Have two cotyledons
-Branched veins
-Ring of vascular bundle
-Usually 4 or 5 fold symmetry (flowers)

Question 4

What is a meristem and what are the different types?

Answer 4

-The point of cell division
-Apical meristem (at the tip causing upward growth)
-Lateral meristem (at the sides causing secondary thickening)
-Intercalary meristem (at the base causing growth up from the base)

Question 5

Origins of grasses.

Answer 5

-Appeared during the Cretaceous
-Dominated the Paleogene (66-23Ma)

Question 6

What features of grasses which have allowed them to become dominant in the modern world?

Answer 6

-Short height (more efficient)
-Phytoliths (Silica crystals which grind away animals teeth making grass grazing tolerant)
-Intercalary meristem (fire and grazing resistant)

Question 7

Australopithecus

Answer 7

Early hominins such as Australopithecus exhibit a combination of bipedal movement and adaptations for climbing. These species lived around 3-4 million years ago.

Question 8

Sahelanthropus

Answer 8

-Early primate
-7Ma from Chad
-Had a small brain and short teeth

Question 9

Homo Erectus

Answer 9

-1.2Ma-140KYrs
-Larger brain
-Spread out from Africa
-Advanced tool use and fire control

Question 10

What has happened to brain size in the last 800 KYrs?

Answer 10

Brain size boomed and has since plateaued as brains bigger brains are energetically expensive and harder to birth.

Question 11

What caused the increase in brain size?

Answer 11

The development of tools and complex social networks.

Question 12

What is the biological species concept?

Answer 12

Species are defined reproductively isolated.

Question 13

Who are we?

Answer 13

-Homo sapiens interbred with Neanderthals in Europe and Asia and Denisovans in Asia.
-Modern humans carry a DNA from these groups
-Therefore there is a more fluid concept of species in human evolution, with overlapping populations rather than strictly separated branches.

Question 14

Homo Sapiens

Answer 14

Homo sapiens is the sole surviving species of the genus Homo.