Adaptations for Nutrition

Question 1

what does it mean for an organism to be single -celled?

Answer 1

they have a large surface area to volume ratio

Question 2

what example of a protoctist uses holozoic nutrition?

Answer 2

amoeba

Question 3

what three ways does an amoeba obtain nutrients such as oxygen and glucose through their cell membranes?

Answer 3

diffusion
facilitated transport
active transport

Question 4

how do amoebas take in food?

Answer 4

they take in large food molecules such as bacteria and microscopic algae via endocytosis
the food molecules are surrounded by membranes, forming vacuoles
the food vacuoles fuse with lysosomes containing hydrolytic enzymes which digest the contents of the food vacuoles
the products of digestion are then absorbed into the cell cytoplasm
indigestible remains are egested by exocytosis

Question 5

describe hydra

Answer 5

they are multicellular fresh water animals
they are in the same phylum as jellyfish
they are cylindrical in shape and have tentacles at the top of the body which contain stinging cells
they have an undifferentiated digestive system

Question 6

label the hydra

Answer 6

tentacle
mouth
hollow body cavity in which digestion occurs
jelly layer
ectoderm
endoderm

Question 7

how do hydra take in food?

Answer 7

their tentacles move paralysed prey in through the mouth and into the sac-like hollow body cavity where the prey is digested
the products of digestion are absorbed into the body cells and the indigestible remains are egested through the mouth
they therefore have only a single opening in their digestive system

Question 8

what is a tube gut?

Answer 8

it is found in most animals and has two openings: mouth and anus

Question 9

what is a sac-like body cavity?

Answer 9

found in hydra and only contains one opening which is the mouth

Question 10

describe tube gut in animals

Answer 10

most animals have a distinct anterior and posterior end and a digestive system that is a tube with two openings
food is ingested at the mouth and the indigestible waste is egested at the anus

Question 11

why must food be digested? give two points

Answer 11

food molecules are insoluble and are too large to cross membranes and be absorbed into the bloodstream

polymers must be converted to their monomers so they can be rebuilt (assimilated) into molecules needed by body cells

Question 12

what are the four main functions of the human gut?

Answer 12

ingestion
digestion
absorption
egestion

Question 13

what two types of digestion?

Answer 13

mechanical digestion

chemical digestion

Question 14

what is the function of ingestion?

Answer 14

taking food into the body through the mouth

Question 15

what is the function of digestion?

Answer 15

the breakdown of large insoluble molecules into soluble molecules that are then small enough to be absorbed into the blood

Question 16

what is the function of mechanical digestion?

Answer 16

cutting and crushing by teeth and muscle contractions of the gut wall, increasing the surface area over which enzymes can act

Question 17

what is the function of chemical digestion?

Answer 17

breakdown using digestive enzymes and bile and stomach acid also contribute to this

Question 18

what is the function of absorption?

Answer 18

the passage of small soluble molecules and ions through the gut wall into the blood

Question 19

what is the function of egestion?

Answer 19

the elimination of indigestible waste eg cellulose (dietary fibre)

Question 20

describe the gut and what two functions of the human gut happen in the gut?

Answer 20

digestion and absorption occur in the gut
the gut is a long, hollow, muscular tube
it allows the movement of its contents in one direction only
each section is specialised and forms particular steps in the processes of mechanical and chemical digestion and absorption

Question 21

what causes the food in the gut to propel along?

Answer 21

peristalsis

Question 22

what is peristalsis and mention dietary fibres?

Answer 22

it is the wave of muscular contractions and relaxations of the gut wall which propel the contents along the whole length of the gut

circular muscles contract behind the bolus of food and then relax after the wave of contraction has passed

dietary fibre aids peristalsis in the intestines

Question 23

give 3 steps of peristalsis

Answer 23

there is a longitudinal muscle and a circular muscle, longitudinal is on the outer layer and circular is on the inner

step 1 - contraction of circular muscles behind food

step 2 - contraction of longitudinal muscles ahead of food

step 3 - contraction in the circular muscle layer forces food forward

Question 24

label the human digestive system (alimentary canal)
there are 14

Answer 24

salivary glands
mouth
epiglottis
esophagus
stomach
liver
gall bladder
pancreas
small intestine:
duodenum
ileum
large intestine (colon)
rectum
anus

Question 25

what is the function of the mouth?

Answer 25

ingestion
mechanical digestion of food due to the crushing action of the teeth
chemical digestion of starch by salivary amylase

Question 26

what is the function of the esophagus?

Answer 26

carriage of food to the stomach by peristalsis

Question 27

what is the function of the stomach?

Answer 27

contraction of stomach muscles to churn up the food aka mechanical digestion
secretion of hydrochloric acid
chemical digestion of proteins by enzymes

Question 28

what is the function of the duodenum?

Answer 28

receives pancreatic juice from the pancreas and bile from the gall bladder
chemical digestion of carbohydrates, fats and proteins by enzymes

Question 29

what is the function of the ileum?

Answer 29

chemical digestion of carbohydrates, fats and proteins by enzymes
absorption of digested food

Question 30

what is the function of the colon?

Answer 30

absorption of water

Question 31

what is the function of the rectum?

Answer 31

storage of feces

Question 32

what is the function of the anus?

Answer 32

site of egestion