B2.2 The challenges of size

Question 1

What is a surface area to volume ratio?

Answer 1

The surface area per unit volume of an object - calculated as a ratio

Question 2

Why is surface area to volume ratio important?

Answer 2

The smaller the organism the larger the SA:V ratio is, nutrients can diffuse directly into the organism quickly enough to sustain life as diffusion distances are small
- larger organism has lower SA:V ratio - most multicellular organisms cant use simple diffusion to survive, as diffusion over a greater distance ant occur fast enough to meet cells demands

Question 3

Exchange surfaces in larger organisms

Answer 3

Larger organisms have developed exchange surfaces, which increase SA:V ratio - e.g. alveoli on lungs, villi of small intestine

Question 4

What features make an efficient exchange surface?

Answer 4

• large SA - so diffusion happens faster
• good blood supply - to maintain a steep concentration gradient so molecules can diffuse quicker
• thin walls - short diffusion distance
• moist - gases can only diffuse dissolved in solution

Question 5

Why do we need a transport system?

Answer 5

• once substance have diffused into the body they must be transported to the cells that need them
• our circulatory system allows materials to travel around our bodies quickly

Question 6

What is the circulatory system made of?

Answer 6

Heart, blood and blood vessels

Question 7

Is the circulatory system open or closed, and why?

Answer 7

Closed - as blood remains within the structures

Question 8

What does the circulatory system transport, and where?

Answer 8

• oxygen & glucose to the cells that need it

- Carbon dioxide and urea (waste products) away from cells

Question 9

What is the heart?

Answer 9

A pump which circulates blood

Question 10

What does blood flow away from the heart in?

Answer 10

Arteries

Question 11

What does blood flow towards the heart in?

Answer 11

Vein

Question 12

Where are valves and what do they do?

Answer 12

They are in the veins, and prevent back-flow of blood, TMT the blood flow is one-way

Question 13

is our circulatory system double or single?

Answer 13

double - blood flows at low pressure from right side (to lungs) & high pressure from left side (to body)

Question 14

is the heart a single or double pump?

Answer 14

double pump

Question 15

describe the flow of blood throughout the body (oxygenated / deoxygenated blood - simple)

Answer 15

• deoxygenated pumped from heart to lungs
• blood receive oxygen - oxygenated blood pumped back to heart to rest of body
• oxygen leaves blood (for respiration in body) + blood goes back to heart

Question 16

what is meant by a closed system?

Answer 16

blood stays inside blood vessels

Question 17

what is the heart made up of?

Answer 17

cardiac tissue

Question 18

what is special about the cardiac muscle?

Answer 18

can contract without receiving a nerve impulse from brain and don’t get tired easily (like other muscles

Question 19

what are the two top chambers of the heart called?

Answer 19

atria (sing. atrium)

smaller

Question 20

what are the two bottom chambers of the heart called?

Answer 20

ventricles

larger

Question 21

label a heart diagram

Question 22

describe the flow of blood through the heart - for oxygenated blood

Answer 22

PV,LA,BV,LV,AO,Body

Question 23

describe the flow of blood through the heart - for deoxygenated blood

Answer 23

VC,RA,TV,RVPA,Lungs

Question 24

characteristics of arteries

Answer 24

• thick walls
• small lumen
• high pressure
• away from heart - oxygenated blood

Question 25

characteristics of veins

Answer 25

- thin walls - large lumen - low pressure - into heart - deoxygenated blood

Question 26

characteristics of capillaries

Answer 26

- very thin walls - one cell thick- - quicker diffusion for gaseous exchange - very small lumen - connected arteries to veins

Question 27

what is blood made of?

Answer 27

platelets plasma red & white blood cells

Question 28

what is plasma?

Answer 28

- pale yellow liquid - makes 55% volume of blood - over 90% water containing dissolved substances such as - food (glucose +amino acids), wastes (urea +CO2), hormones and antibodies

Question 29

where are red blood cells made?

Answer 29

in bone marrow + live for about 4 months

Question 30

what is the role of red blood cells?

Answer 30

carry O2 from lungs to organs

Question 31

what are adaptations of red blood cells?

Answer 31

- biconcave disks - larger SA:V ratio - quicker diffusion of O2 - have lots haemoglobin which carry O2 - no nucleus - more space for haemoglobin + can carry more O2

Question 32

what are platelets?

Answer 32

small fragments of cells - no nucleus - help blood clot at wounds

Question 33

what are white blood cells?

Answer 33

- part of body defence system against pathogens | - have nucleus

Question 34

what are coronary arteries

Answer 34

- supply blood to heart muscle | - wrap around outside of heart - small branches dive into blood

Question 35

what is most of the heart made up of?

Answer 35

- cardiac muscle / tissue