Endosymbiotic theory and cell differentiation

Question 1

from what kind of a common ancestor have eukaryotes evolved

Answer 1

one-celled with nucleus
anaerobic
reproduced either asexually by mitosis or sexually by meiosis and fertilization

Question 2

how were mitochondria formed

Answer 2

by endocytosis of aerobic heterotrophic bacteria by the common ancestor

Question 3

how were chloroplasts formed

Answer 3

by endocytosis of photoautotrophic bacteria by the common ancestor

Question 4

how did both organisms benefit from endosymbiosis (mitochondrion)

Answer 4

bacteria giving the common ancestor a supply of ATP produced more efficiently than by anaerobic CR
bacteria provided with food allowing it to grow and divide, being passed on to daughter cells
- eventually became codependent

Question 5

evidence for endosymbiotic theory

Answer 5

70S ribosomes
double membrane (vacuole)
circular, naked DNA
divide by binary fission (mitochondria)

Question 6

what is cell differentiation

Answer 6

when cells develop along different pathways despite the same genome

Question 7

reason for cell differentiation

Answer 7

different gene expression due to different chemical signals in the cells’ environment that impact it

Question 8

how are tissues formed

Answer 8

groups of cells in the same environment (area) get influenced by the same chemicals and express the same genes (specialize for the same function)

Question 9

how do cells of the same tissue interact

Answer 9

interacting and connecting to each other by cell-to-cell adhesion proteins (integrity of the tissue maintained)
- in all tissues except blood

Question 10

housekeeping genes

Answer 10

genes active in all cells which are required for basic life processes

Question 11

why are some genes expressed in only some cells
give an example

Answer 11

because they cause the development of specialized structures
e.g. genes for the synthesis of hemoglobin are only expressed during the development of red blood cells

Question 12

advantages of cell differentiation

Answer 12

• form can match function more specifically
• specialist performs a function of life more efficiently than a generalist

Question 13

advantages of multicellularity

Answer 13

• longer lifespan of the organism (death of one cell does not impact survival of the whole organism)
• larger body size possible (plants competing for light, predatory animals)
• effectiveness due to cell differentiation (more complex body forms can develop)