Plant Evolution

Question 1

What is the structure of byrophytes?

Answer 1

Never have roots, contain rhizoids, simple leaves and stems are non-vascular

Question 2

What is the structure of filicinophytes?

Answer 2

Vascular roots, leaves & non-woody stems

Question 3

What is the structure of conferophytes?

Answer 3

Trees or shrubs with woody vascular tissues, narrow leaves with thick waxy cuticle

Question 4

What is the structure of angiospermophytes?

Answer 4

Roots, leaves and stems, vascular tissue, some stems are herbaceous others woody

Question 5

What adaptations of vascular plants has helped their success on land?

Answer 5

Regional specialization of body; roots stems and leave. Structural support to stand on land. Vascular system. Pollen, eliminated need for water to transport gametes, seeds, and dominance of sporophyte

Question 6

Draw and label the distribution of tissues in the stem

Answer 6

Refer to image

Question 7

Explain the relationship between the distribution of tissues in the leaf and the functions of these tissues

Answer 7

Epidermis on the outside: Stomata on underside of leaf; allows exchange of gases

Ground tissue: palisade parenchyma = site of most photosynthesis. Spongy parenchyma =
gases circulate.

Vascular tissue: branches into leaf traces for support and improved transport of water/nutrients

Question 8

What are three characteristics of monocotyledonous plants?

Answer 8

embryos have one cotyledon, leaf has veins that are usually parallel, stems are vascular bundles usually complexly arranged

Question 9

What are three characteristics of dicotyledonous plants?

Answer 9

embryos have two cotyledons, leaves have veins that are usually netlike, and stems are vascular bundles usually arranged in a ring

Question 10

What is the function of apical meristems in dicots?

Answer 10

Allow plant to grow in length and serves as the primary growth

Question 11

What is the function of lateral meristems in dicots?

Answer 11

Allows the plant to grow in girth (stems in woody plants) serves as the secondary growth

Question 12

Explain the role of auxin in phototropism as an example of the control of plant growth

Answer 12

Auxin is responsible for promoting elongation on the shaded side of a plant stem. This allows the stem to grow towards the light source. The hormone accumulates on the shaded side, causing cells on that side to grow longer and thus bending the stem towards the light.

Question 13

What is a storage organ?

Answer 13

A storage organ is a part of a plant specifically modified to store energy (e.g. carbohydrates) or water

Question 14

Where are the storage organs in plants found?

Answer 14

They are usually found underground (better protection from herbivores) and may result from modifications to roots, stems or leaves:

Question 15

What is a storage root?

Answer 15

Modified roots that store water or food (e.g. carrots)

Question 16

What are stem tubers?

Answer 16

Horizontal underground stems that store carbohydrates (e.g. potato)

Question 17

What are bulbs?

Answer 17

Modified leaf bases (may be found as underground vertical shoots) that contain layers called scales (e.g. onion)

Question 18

How do succulents enable water storage?

Answer 18

modified leaves or stems (thickened, fleshy and wax-covered) to enable water storage

Question 19

How do other plants modify to support climbing and attachment? What is this modification called?

Answer 19

Other plants (e.g. vines) have modifications to their leaf or stem to enable climbing support and attachment - these are called tendrils

Question 20

Outline four adaptations of xerophytes

Answer 20

small or compound leaves, deep root systems, spines, waxy cuticle development, and a variety of stomata adaptations.

Question 21

State the significance of thickened cellulose in terrestrial plants

Answer 21

Thickening of the cell wall provides extra structural support

Question 22

State the significance of cell turgor in terrestrial plants

Answer 22

Increased hydrostatic pressure within the cell exerts pressure on the cell wall, making cells turgid

Question 23

State the significance of lignified xylem in terrestrial plants

Answer 23

Xylem vessels run the length of the stem and branches, lignification of these vessels provides extra support

Question 24

Explain how the root system provides a large surface area for mineral ion and water uptake

Answer 24

Plants take in water and essential minerals through their roots; thus need a large surface area in order to optimize the uptake. The ‘extensive’ branching of the roots and the growth of root hairs allows for the plant to increase its mineral ion absorption and surface area of water.

Question 25

List three ways in which mineral ions in the soil move to the root

Answer 25

Diffusion, mass flow, and fungal hyphae

Question 26

What is diffusion?

Answer 26

Movement of minerals along a concentration gradient

Question 27

What is mass flow?

Answer 27

Uptake of mineral ions by means of a hydrostatic pressure gradient

Question 28

What is Fungal Hyphae

Answer 28

Absorb minerals from the soil and exchange with sugars from the plant (mutualism)

Question 29

Define transpiration

Answer 29

Transpiration is loss of water from the stomata of leaves

Question 30

Explain how guard cells regulate transpiration

Answer 30

Stomata consist of microscopic pores, each flanked by a pair of guard cells. Guard cells can increase or decrease the size of the pore via changes in their turgor status, hence regulating both CO2 entry into the leaf and transpiration, or the loss of water from the leaf.

Question 31

State the function of abscisic acid in regulating the stomata

Answer 31

A typical effect of ABA on leaves is to reduce transpirational water loss by closing stomata and parallelly defend against microbes by restricting their entry through stomatal pores.

Question 32

Explain how abiotic factors (light temperature wind and humidity) affect the rate of transpiration

Answer 32

High temperatures increase evaporation rate of water.

High humidity lowers the rate of water evaporation.

High light intensity usually increases photosynthesis which increases transpiration.

Question 33

Outline the role of phloem in active translocation of sugars and amino acids from source to sink

Answer 33

Phloem tissue transports sugars and amino acids from sources which include photosynthetic tissue (leaves and stems) and storage organs, to sinks which include the fruits, seeds and roots of the plant.

This transport is known as active translocation and requires energy.

Question 34

Draw and label the structure of a dicotyledonous animal-pollinated flower

Answer 34

refer to image

Question 35

Define pollination

Answer 35

the placement of pollen on the stigma. The transfer of pollen grains from the anther to the stigma (usually of another plant), often facilitated by animals, wind or water movement

Question 36

Define fertilization

Answer 36

a process of sexual reproduction, which occurs after pollination and germination. Fusion of the male gamete nuclei (in the pollen grain) with the female gamete (in the ovule) to form a zygote

Question 37

Define seed dispersal

Answer 37

Fertilized ovules form seeds that move away from the parental plant before germination, reducing competition for resources

Question 38

Draw and label a diagram of the internal and external structure of a named dicotyledonous seed

Answer 38

refer to image

Question 39

Describe the metabolic events of germination in a typical starchy seed

Answer 39

The absorption of water followed by the formation of gibberellin in the emery cotyledon, This stimulates the production of amylase which catalyzes the breakdown of starch into maltose. This maltose then diffuses to the embryo for energy release and growth

Question 40

Explain the conditions needed for the germination of a typical seed

Answer 40

Germination is the emergence and growth of an embryonic plant from a seed. Water is needed to metabolically activate the cells, proper temperature for optimal functions of enzymes, and oxygen for aerobic respiration (need ATP in order to grow).

Question 41

What happens if the conditions for germination of a typical seed are not favorable?

Answer 41

If conditions are not favorable then the seed may remain dormant. This way the seed can survive adverse conditions and only start to germinate when conditions become favorable.

Question 42

Explain how flowering is controlled in long-day and short-day plants

Answer 42

Flowering in long-day and short-day plants is controlled by a pigment called phytochrome. This pigment exists in two forms, P(sub)r and P(sub)fr which can be converted into each other.

Question 43

What is P(sub)fr and P(sub)r?

Answer 43

The Pfr form is the active form of phytochrome, while the Pr form is the inactive form of phytochrome

Question 44

When does P(sub)fr and P(sub)r, convert into each other?

Answer 44

Sunlight contains more red light, so the Pfr form is predominant during the day, with the gradual reversion to the Pr form occurring at night

Question 45

When is flowering induced in long day plants?

Answer 45

In long day plants, the active Pr form is a promoter of flowering and so flowering is induced when the night period is less than a critical length and Pfr levels are high

Question 46

When is flowering induced in short day plants?

Answer 46

In short day plants, the active Pfr form is an inhibitor of flowering and so flowering is induced when the night period is greater than a critical length and Pfr levels are low

Question 47

How does the structure of xylem vessels aid the transpiration stream?

Answer 47

The outer cell walls contain thickenings which resemble spirals/rings with lignin which makes the vessels strong and able to withstand low pressures.

Question 48

How does evaporation aid the transpiration stream?

Answer 48

Due to evaporation of water from the leaf, the transpiration pull occurs (more water to be pulled up xylem tube due to low pressure)

Question 49

How does cohesion/adhesion aid the transpiration stream?

Answer 49

Columns of water do not break due to cohesion and adhesion of water molecules (cohesion of water molecules and adhesion of water molecules to walls of xylem)

Question 50

What is transpiration pull?

Answer 50

low pressure causes more water from the roots to be pulled upwards through the xylem tubes, this is called transpiration pull.