Eukaryotes

Question 1

What does endosymbiotic theory suggest?

Answer 1

That smaller, aerobic bacteria were engulfed & these persisted & reproduced within the cytoplasm.

Question 2

What is symbiosis?

Answer 2

When 2 different species benefit from living & working together.

Question 3

What is endosymbiosis?

Answer 3

Where one of those organisms is inside the other organism.

Question 4

What does the ‘host’ gain from endosymbiosis?

Answer 4

Gains products of aerobic respiration (via mitochondria) or phs (via chloroplasts), which fuels their metabolism

Question 5

What does the ‘symbiont’ gain from endosymbiosis?

Answer 5

Protection

Question 6

Give 3 pieces of evidence that support endosymbiotic theory.

Answer 6

• Mitochondria & chloroplasts are an appropriate size to have been independent unicellular organisms
• They are affected by antibiotics specifically targeted at prokaryotes
• They have distinct DNA present in a single loop which is inherited cell to cell

Question 7

Where does phs take place in prokaryotes?

Answer 7

Thylakoids

Question 8

Where does phs take place in eukaryotes?

Answer 8

Chloroplasts (thylakoids)

Question 9

What is primary endosymbiosis?

Answer 9

Occurs when chloroplasts have 2 membranes

Question 10

What is secondary endosymbiosis?

Answer 10

Occurs when there are 3 or 4 membranes

Question 11

Give 4 hypotheses regarding the cause of the Cambrian explosion

Answer 11

1- New predatory-prey relationships →diversity
2- Increases in atmospheric O2 → success of animals with higher metabolic rates
3- Increased nutrient availability and change of seawater composition → environmental triggers e.g. minerals washed out of soils into ocean after Snowball Earth thaw
4- Related to molecular evolution: the Cambrian Period corresponds with the timing of the evolution of the Hox gene complex.
Determines body development in the embryo e.g. limb position → Enhanced the potential for evolution of segmented
body plans