Lecture 13

Question 1

Gymnosperms are

Answer 1

Seed-forming, non-flowering plants

Question 2

Development of pollen and seeds in gymnosperms removed

Answer 2

the requirement of water for reproduction

Question 3

Pollen

Answer 3

Tiny capsule which contains the male gametophyte and the sperm produced by the gametophyte - dispersal by wind and sometimes animals

Question 4

Seed

Answer 4

Sporophyte embryo packaged into a hard shelled capsule with food - dispersal by wind and sometimes animals

Question 5

Cones

Answer 5

Scaly sporophylls produced by gymnosperms
Two types of cones are produced: Female and male

Question 6

Prefixes used to refer to the gender of cones

Answer 6

Micro: Male reproductive structures
Mega: Female reproductive structures

Question 7

Male cones

Answer 7

Contain the microsporophylls (2n) which contain the microsporangium (2n)

Question 8

Microsporangium (2n) produces

Answer 8

Microspores (n) via meiosis which grow into the male gametophyte (n) and produces the sperm (n)
- Male gametophyte and sperm is packaged into a pollen and dispersed by wind

Question 9

Female cone are the

Answer 9

Megasporophylls (2n) which contain the megasporangium (2n)

Question 10

Megasporangium (2n) produces

Answer 10

megaspores (n) via meiosis which grow into the female gametophyte (n) and produces the egg (n)

Question 11

The megasporangia and the megaspore (n) is contained in the

Answer 11

protective integument
Ovule = Integument + Megasporangium + megaspore

Question 12

How does the ovule develop into a seed after pollination

Answer 12

After pollen grain attaches to the ovule (pollination), the pollen tube delivers sperm to the egg to produce the zygote (fertilization)

The zygote grows into the embryo which is the ‘baby’ form of the new sporophyte

Other tissues of the female gametophyte becomes the food supply packaged into seed and integument becomes the seed coat

Question 13

Gymnosperm has an extremely

Answer 13

Sporophyte dominated life cycle

Question 14

moss life cycle

Answer 14

Zygote grows into sporophyte -> sporangia (2n) -> Spores (n) -> male and female gametophyte -> fertilized zygote after sperm dispersal

Question 15

Gymnosperm life cycle

Answer 15

Seeds grow into sporophyte (2n) -> Male and female cones contain micro/mega sporangia -> micro/mega spores (n) -> male (contained in pollen) and female (contained in ovule) gametophytes -> fertilized zygote grows into embryo packaged into seeds after pollen dispersal by wind

Question 16

Major difference between gymnosperm and angiosperm

Answer 16

Gymnosperm (pines)
- “naked seed”
- Ovule is exposed to the environment
- Upon pollination, ovule develops into seed

Angiosperm (flowering plants)
- “container seed”
- Ovule is encased inside the ovary
- Upon pollination, ovule develops into the seed, ovary develops into the fruit

Some gymnosperms produce a fleshy fruit like structure but is not a true fruit as it is not derived from an ovary

Question 17

Juniper berry

Answer 17

• Allows Seed dispersal by animals
• Convergent evolution, acquiring the same function as the fruits produced by angiosperms

Question 18

Angiosperms are

Answer 18

Seed forming, flower and fruit forming plants

Development of flowers and fruits allowed angiosperms to take full advantage of the terrestrial environment

Some pollen and seeds (fruits) specialized for dispersal by animals but others disperse by wind

Question 19

How do flowers make animals help pollination

Answer 19

• Unique structure to facilitate pollination via animals

Sepal: Base of the flower, enclosed the flower before it opens

Petal: Brightly coloured portion of the flower to attract pollinators

Question 20

Flowers and pollination: Stamen and Carpel

Answer 20

Stamen: Male reproductive organ
- Anther contains microsporangia to produce pollens
- Filament is the supportive structure with anther on its end

Carpel: Female reproductive organ
- Stigma is the sticky tip of carpel to capture pollens
- Style connects the stigma to the ovary
- Ovary is the base of carpel that contains the ovules
Ovule (contained in ovary) = Integument + megasporangia + megaspore

Question 21

Pollination and production of seed and fruit

Answer 21

Pollen grain on anther gets dispersed by animals/wind
Pollen lands on the stigma of the carpel (pollination)
- Pollen tube grows from the pollen to the ovule to deliver the sperm to egg

As with gymnosperms, the ovule develops into the seed the contains the embryo
Ovary of the flower devlops into the fruit

Question 22

Flowers life cycle

Answer 22

1. Megasporangium in each ovule produces megaspore. Megaspores grows into female gametophyte which produces egg.
2. Microsporangium in the anther produces microspores.
3. Microspores develops into male gametophytes, which gets packaged into pollen alongside its sperm. Pollen gets delivered to stigma (pollinization) and pollen tube begins to grow.
4. Pollen tube reaches the ovary and delivers sperm to the ovule.
5. Fertilization of egg and sperm into zygote.
6. Zygote develops into the embryo. Other parts of ovule develops into the seed. The
   ovary develops into the fruit.
7. Seed gets dispersed and grows into the ‘mature plant’ (sporophyte).

Question 23

Flower diversity

Answer 23

Is the result of angiosperms taking advantage of the various creatures on terrestrial land to facilitate pollination

Question 24

Fruits

Answer 24

Develop from ovaries to encase the seed
- protects the seeds and help with dispersal

Can be fleshy or dry
flesh fruits: tomatoes
Dry fruits: beans, nuts

Question 25

Fruit dispersal

Answer 25

Dispersal by animals - Eaten by animals and the undigested seed gets released with feces - Stored underground by animals - Sticks onto animals to get carried around Dispersal by wind - Dandelion fruit

Question 26

Different types of fruits

Answer 26

Simple fruit - Derived from a single carpel or several fused carpels Aggregate fruit - Derived from a single flower with a group of individual carpels each forming a small fruitlet - Fruitlets become clustered together Multiple fruit - Derived from group of flowers clustered together - Ovaries mature and fuse together into one fruit Accessory fruit - Other parts of flower develop into what humans perceive as the 'fruit'

Question 27

Apple is an

Answer 27

accessory fruit - The core of the apple is its actual fruit, developed from the ovule - Majority of the fleshy, edible portion is derived from the receptacle (flesh) tissue which surrounds the ovule

Question 28

Dandelion produces multiple

Answer 28

clustered fruits from multiple clustered flowers

Question 29

Dandelion fruit is

Answer 29

Specialized for wind dispersal, floating in the air - White wings are called pappus - Single dandelion fruit develops from one flower and its ovary - Single dandelion seedhead develops with many fruits attached to it

Question 30

The dandelion 'flower' is not

Answer 30

a single flower, it is many small florets clustered together Each seedhead contains about 40-100 florets

Question 31

Roots

Answer 31

Anchors vascular plant in soil and absorbs mineral and water Often stores carbohydrates and other reserves for plant to use Carrots stores food directly in their root (root veggies) Potatoes are tubers which store food in specialized structures which developed from parts of their root

Question 32

Roots and the nitrogen cycle

Answer 32

Plants use roots to absorb nitrogenous compounds in soil such as NO3 nitrate plus ammonium NH4 Soil living nitrogen fixing bacteria fix nitrogen gas in the atmosphere to ammonia - Some of these nitrogen fixing bacteria are free living whereas others form a symbiotic relationship with certain types of plants

Question 33

Example of nitrogen fixation with bacteria of Rhizobium sp.

Answer 33

Bacteria coexists inside specialized root nodules where growing plant invites the bacteria to infect their root while the bacteria also emits chemicals to facilitate the process The infected area develops into nodules for rhizobium to live inside A vascular system is then established between the nodule and root for nutrient exchange The nodule provides an anaerobic environment for rhizobium to fix nitrogen whereas the plant also provides other nutrients to keep bacteria population healthy

Question 34

Examples of legume plants that can form a mutalistic relationship between nitrogen fixing bacteria

Answer 34

Beans, lentils, chickpeas

Question 35

Crop rotation

Answer 35

Many commercially important crops such as wheat absorb nitrogen from soil Growing the same crop in the same field over time depletes essential nutrients Other crops such as legumes can add nitrogen to soil via their mutualistic nitrogen fixing bacteria Crop rotation: Plant nitrogen-absorbing crops and legumes in a rotation to help sustain the nutrient content of the field

Question 36

Three field crop rotation

Answer 36

First field: Nitrogen depleting crops such as wheat Second field: Legumes such as peas and beans Third field: No crop planted. The field gets overgrown by weeds. Animals are grazed on this land to add more nutrients via their feces Crop rotation drastically increases the amount of crop yield while reducing the need for artificial fertilizers