3.1.5 Gas Exchange and the Transport of Oxygen in Living Organisms Flashcards Preview

A-level Biology Oxford AQA > 3.1.5 Gas Exchange and the Transport of Oxygen in Living Organisms > Flashcards

Flashcards in 3.1.5 Gas Exchange and the Transport of Oxygen in Living Organisms Deck (87)
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1

Why do organisms need to exchange substances with their environment?

  • Cells need to take in oxygen and nutrients
  • Cells need to excrete waste products (e.g. carbon dioxide and urea)
  • Most organisms need to stay same temperature = heat needs to exchanged

2

Smaller animals have a _____ SA : Volume Ratio

Higher

3

Why do multicellular organisms need exchange organs and mass transport systems?

∵ diffusion across the outer membrane would be too slow

4

Why don't single-celled organisms need exchange organs or mass transport systems?

∵ Substances can diffuse directly into (or out of) cells across cell-surface membrane (diffusion rate is quick)

5

Name 2 things that cause diffusion across outer membrane to be too slow in multicellular organisms

  • Cells deep within body
    • Big distance between them & outside environment
  • Larger animals = low SA:volume ratio

6

What is tissue fluid?

Environment around cells of multicellular organisms 

7

What is the mass transport system in mammals?

Circulatory system

8

What is the mass transport system in plants?

Transport of water and solutes in xylem and phloem

9

Name 2 factors that affect heat exchange

  • Shape
  • Size

10

Animals with compact shape have a ___ surface area relative to their volume which _____ heat loss from their surface

Animals with compact shape have a SMALL surface area relative to their volume which MINIMISIES heat loss from their surface

11

What do small animals (with a large surface area) need to stay warm and why?

High metabolic rate to generate enough heat to stay warm ∵ they lose heat easily

12

Name 3 gas exchange surfaces adaptations

  • Large SA
  • Thin = short diffusion pathway
  • Steep concentration gradient

13

Name 2 ways organisms maintain a steep concentration gradient

  1. Via movement of environmental medium e.g. air
  2. Via transport system = ensure movement of internal medium

14

Name 2 features that single-celled organisms have that allow gases to diffuse through their outer surface

Have large surface area, thin surface & short diffusion pathways

15

Name the main gas exchange surface in dicotyledonous plants

 

Surface of mesophyll cells in leaf

16

Dicotyledonous Plants

Gases move in and out through special pores in epidermis called _____

stomata

17

What do insects use for gas exchange?

Tracheae (microscopic air-filled pipes)

18

What are spiracles?

Pores on insects' surface

19

Describe and explain the movement of oxygen into the gas exchange system of an insect when it is at rest

  1. Oxygen is used in aerobic respiration 
  2. So oxygen concentration gradient established
  3. Oxygen diffuses in through spiracles, then tracheae & then through tracheoles which go into individual cells

20

How is carbon dioxide removed from insects?

 Carbon dioxide from the cells diffuses (down its own concentration gradient) into tracheal tubes and through the spiracles 

 

21

Why do insects have to be small in size?

∵ insects mainly rely on diffusion to exchange gases 

22

What is tracheae supported by to prevent them from collapsing?

Strengthened rings

23

Name 4 adaptations of dicotyledonous plants that enable efficent gas exchange

  1. Many stomata 
  2. Thin, flat shape = provides large SA:volume ratio
  3. Numerous interconnection air spaces throughout mesophyll
  4. Leaf is flattened so no living cell is far form external air

24

Exchanging gases ____ water

loses

25

Name 2 adaptations that insects have to minimise water loss (without reducing gas exchange too much)

  • If insects are losing too much water = close their spiracles using muscles
  • Have waterproof, waxy cuticle over their body & tiny hair around their spiracles = reduce evaporation

26

Name an adaptation of dicotyledonous plants to minimise water loss without reducing gas exchange too much

If plants gets dehydrated = guard cells lose water & become flaccid = closes stomata

27

How are plants' stomata kept open during day (for gaseous exchange)?

Water enters guard cells = making them turgid = opens stomatal pore

28

What type of process is inspiration (breathing in)?

Active process – uses energy

29

What type of process is expiration (breathing out)?

Passive process

30

Describe the process of inspiration

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