1: Unicellular and Multicellular Organisms Flashcards Preview

IB Biology SL > 1: Unicellular and Multicellular Organisms > Flashcards

Flashcards in 1: Unicellular and Multicellular Organisms Deck (36):
1

How many cells in a unicellular organism?

1. one

2

What do unicellular organisms carry out inside them?

1. all the functions of life

3

Give two examples of unicellular organisms.

1. Paramecium
2. Chlamydomonas

4

Where does a Paramecium live? How long is a Paramecium?

1. lives in ponds
2. 0.05mm - 0.33mm long

5

Where does a Chlamydomonas live? How long is a Chlamydomonas?

1. freshwater habitats
2. 0.002mm - 0.010mm

6

Draw a Paramecium. (see p2)

1. cilia
2. contractile vacuole
3. plasma membrane
4. nucleus
5. cytoplasm
6. food in vesicles

7

Draw a Chlamydomonas. (see p2)

In common with Paramecium:

2. contractile vacuole
3. plasma membrane
4. nucleus
5. cytoplasm

Different to Paramecium:

1. flagellum
2. eye spot
3. cell wall
4. chloroplast

8

We are going to compare similarities and differences between Paramecium and Chlamydomonas. What functions of life are we going to compare?

Differences:

1. Nutrition
2. Excretion
3. Growth
4. Response

Similarities:

1. Metabolism
2. Homeostasis
3. Reproduction

9

Compare 'Nutrition' of Paramecium and Chlamydomonas.

1. Paramecium feeds on smaller organisms by ingesting and digesting them in vesicles
2. whereas Chlamydomonas produces its own food by photosynthesis using a chloroplast

10

Compare 'Growth' of Paramecium and Chlamydomonas.

1. Paramecium increasing in size and dry mass by accumulating organic matter and minerals from its food
2. whereas Chlamydomonas increases in size and dry mass due to photosynthesis and absorption of minerals

11

Compare 'Response' of Paramecium and Chlamydomonas.

1. Paramecium reacts to stimuli, e.g. reverses its direction of movement when it touches a solid object
2. whereas Chlamydomonas reacts to stimuli, e.g. senses where the brightest light is with its eyespot and swims towards it

12

Compare 'Excretion' of Paramecium and Chlamydomonas.

1. Paramecium expels waste products of metabolism, e.g. CO2 from respiration diffuses out of the cell
2. whereas Chlamydomonas expels waste products of metabolism, e.g. oxygen from photosynthesis diffuses out of the cell

13

Compare 'Metabolism' of Paramecium and Chlamydomonas.

1. Both produce enzymes which catalyse many different chemical reactions in the cytoplasm

14

Compare 'Homeostasis' of Paramecium and Chlamydomonas.

1. Both keep internal conditions within limits, e.g. expels excess water using contractile vacuoles

15

Compare 'Reproduction' of Paramecium and Chlamydomonas.

1. Both reproduce asexually using mitosis or sexually using meiosis and gametes

16

What happens to a cells surface area to volume ratio as it grows larger?

1. the SA:V decreases

17

What does the rate at which materials enter/leave (a cell) depend on?

1. the surface area of the cell

18

What does the surface area of a cell determine?

1. the rate at which materials enter/leave the cell

19

What does the rate at which materials are used or produced (in a cell) depend on?

1. the volume of the cell

20

What does the volume of a cell determine?

1. the rate at which materials are used or produced

21

What happens if a cell becomes too large?

1. it may not be able to take in essential materials or excrete waste substances quickly enough

22

Why are large organisms multicellular?

Don't try and learn this. Understand why.

1. SA:V decreases as a cell increases
2. if a cell becomes too large, it may not be able to take in essential materials or excrete waste substances quickly enough
3. the cell can no longer survive at this size, so it divides
4. large organisms therefore consist of many cells (multicellular)

23

Name two advantages of being a multicellular organism.

1. cells can take in/excrete essential materials/ waste substances fast enough
2. multicellular allows division of labour, which means different groups of cells can become specialised for different processes

24

Through what process does a cell become specialised?

1. the process of differentiation

25

What do emergent properties arise from?

1. the interaction of the component parts of a complex structure

26

There is a helpful idiom that can summarise 'emergent properties'. What is it?

1. 'the whole is greater than the sum of the parts'

27

What sort of organisms have properties that emerge from the interaction of their cellular components?

1. multicellular organisms

28

Give an example of emergent properties in an organism.

1. a tiger
2. each cell is a unit of life with distinctive properties e.g. sensitivity to light in retina cells
3. individually, the cells can barely do anything
4. together, they comprise an organism that can have a profound ecological impact on its environment

29

Define genome.

1. an organisms entire set of genes

30

What percentage of an multicellular organisms genome is in each cell?

1. 100%

31

In multicellular organisms, 100% of the genome is in each cell. Why is this significant?

1. each cell has the instructions to develop into any type of cell

32

Which genes does a cell use in differentiation?

1. only the genes it needs to follow its pathway of development
2. other genes are unused

33

What is a cell doing when it uses only the genes it needs to follow its pathway of development ?

1. differentiating

34

Give an example of gene expression when a cell is differentiating.

1. the genes for making hemoglobin are only expressed in developing red blood cells

35

What can a cell do/not do once it has begun a pathway of development?

1. it is fixed and cannot change to a different path

36

Once a cell has begun a pathway of development it is said to be...?

1. 'committed' - it cannot change to a different path

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