4

Question 1

coenocytic organisms

Answer 1

nucleus divides multiple times, but the cell does not, so the nuclei are not partitioned into individual cells

Question 2

Selective advantages of simple multicellular organisms

Answer 2

Multicellularity helps organisms avoid getting eaten
May be able to maintain their position on a surface or in the water column better than their single-celled relatives
Feeding (e.g. in colonial heterotrophs the coordinated beating of flagella assists feeding by directing currents of food laden water towards the cells

Question 3

costs associated with multicellularity

Answer 3

For complex multicellular organisms with differentiated reproductive tissues, most cells do not reproduce, instead supporting the few that do
This requires cooperation among cells, but it creates opportunities for cells to ‘cheat’- use nutrients for their own proliferation rather than the growth and reproduction of the organism as a whole
Cancer is the most conspicuous and lethal example of non-cooperation, the defining disease of complex multicellular organisms

Question 4

3 general features of complex multicellularity

Answer 4

Highly developed molecular mechanisms for adhesion between cells
Display specialised structures that allow cells to communicate with one another
Display complex patterns of cellular and tissue differentiation, guided by networks of regularly genes

Question 5

endosymbiosis evidence

Answer 5

Two layers of membrane on mitochondria (outer from bacteria being engulfed, made of phospholipids like eukaryotic cell whereas inner membrane like prokaryotic cell’s)
Has its own single circular genome
Mitochondrial genes more similar to prokaryotic genes
Other organelles then developed