Lecture 12

Question 1

Plants (embryophytes) are members of

Answer 1

Archaeplastida, sister group to charophyte algae

Question 2

List the similarities between plants and algae

Answer 2

• Eukaryotic photoautotrophs
• Multicellularity
• Alternation of generations
• Plastid which has a cyanobacterial ancestry
• Cellulose cell walls

Question 3

How is cyanobacterial ancestry acquired

Answer 3

Directly by primary endosymbiosis or indirectly by secondary endosymbiosis

Question 4

Distinguishing feature of plants vs algae

Answer 4

Plants occupy land while all algae are aquatic

Question 5

What is the major advantage of land

Answer 5

• Easier access to sunlight
• Sunlight gets absorbed extremely easily by water
• Better access to soil, minerals

Question 6

Earth’s dense atmosphere (statosphere/ troposphere) is about

Answer 6

50 km thick
- 50% of sunlight from outer space reaches earth’s surface after travelling through this atmosphere

Question 7

What happens once sunlight enters water

Answer 7

50% of it gets lost/ absorbed after the first 10 meters

Question 8

terrestrial habitat

Answer 8

any environment that exists on land—as opposed to in water (aquatic habitat) or air. It includes places where organisms live and interact with their surroundings on the Earth’s surface

Question 9

Challenges of terrestrial habitats

Answer 9

• Lack of water
• Limited water supply for photosynthesis
• No protection against desiccation (loss of moisture)
• Less support against gravity
• No water for spores and sperms to swim in

Question 10

Dispersal of spores and sperms is completely

Answer 10

Water dependent for Brown algae since they can swim in the water to disperse

Question 11

What does sporangia of algae develop

Answer 11

Surface of blade to produce zoospores

Question 12

What specialized tissues did plants evolve to occupy above and under the ground

Answer 12

Leaves: Acquire sunlight and CO2 from above ground

Roots: Acquire water and minerals from underground

Vascular system: Transports these products through plant body

Question 13

Plant dispersal mechanisms that do not depend on water

Answer 13

Pollens: Male gametophyte packaged into shelled structures to disperse sperms via air/animals

Seeds: Developing embryo packaged with a protective coating + food source, dispersal via air/animals

Question 14

List the multistep process in how plants evolved land conquering traits

Answer 14

Step 1: Mosses; Basic traits to persist on land
Step 2: Ferns; traits to combat gravity
Step 3: Pines; traits to reproduce without water
Step 4: Flowers; traits to take full advantage of the terrestrial environment
- During this process, the alternation of generation changed from a gametophyte-dominated cycle to an extremely sporophyte dominated cycle

Question 15

List all the non vascular plants

Answer 15

• Liverworts
• Mosses
• Hornworts

Question 16

List all the seedless vascular plants

Answer 16

Lycophytes (club mosses)
Monilophytes (ferns)

Question 17

Seed plants

Answer 17

Gymnosperms
Angiosperms

Question 18

Explain step 1 of plant evolution

Answer 18

Representative plant: Moss
Group name: Non vascular plants (bryophytes)
Land conquering trait: Anti desiccation mechanisms
Sperm dispersal: Water
Dominance of life cycle: Gametophyte
Other members: Liverworts

Question 19

Explain step 2 of plant evolution

Answer 19

Representative plant: Ferns
Group name: Seedless vascular plants
Land conquering traits: Vascular system and tissue specialization
Sperm dispersal: Water
Dominance of life cycle: Extremely sporophyte
Other members: Club mosses, horsetails

Question 20

Explain step 3 of plant evolution

Answer 20

Representative plant: Pines
Group name: Gymnosperms: Vascular seed plant
Land conquering trait: Pollen, ovule, seed
Sperm dispersal: Mainly wind
Dominance of life cycle: Extremely sporophyte
Other members: Spruces, firs

Question 21

Explain step 4 of plant evolution cycle

Answer 21

Representative flower: Flowers
Group name: Angiosperms: Vascular flowering seed plants
Land conquering trait: Flower and fruit
Sperm dispersal: Wind or animal
Dominance of life cycle: Extremely sporophyte
Others members: too many to list..?

Question 22

About 90% of plant species are

Answer 22

Angiosperms: It shows how successful their strategy to occupy diverse niches on land
- Other plants are also competitive and effective (pine forest) but not as diverse

Question 23

Mosses and protection from desiccation

Answer 23

Use of sporopollenin to cover the spores for protection against desiccation; remember charophyte algae covers their zygotes

Cuticles: Waxy polymer covering plant body for protection against desiccation

Stomata: Pores on plant surface for CO2 and O2 exchange… Closes in dry conditions to preserve water
- Traits allow mosses to persist on land

Question 24

Mosses and protection from desiccation pt2

Answer 24

• Lack of further specialized tissues limit mosses from growing tall
• No hardened tissues to support body against gravity
• No vascular structure to transport water and nutrients throughout the body
• No true root; Moss use rhizoids to anchor onto surface, rhizoids do not transport water

Question 25

Moss life cycle

Answer 25

- Gametophyte dominated alternation of generations - Moss gametophyte: The green 'mossy' things which we typically of as a moss

Question 26

Moss sphorophyte

Answer 26

Appendages which grow out from the gametophyte - Has the sporangium (the spore producing tissue) at the end - Completely dependent on the gametophyte for growth and survival - Usually has a shorter life than the gametophyte

Question 27

Explain the process of moss life cycle

Answer 27

1. Moss spores grow into protonemata 2. Protonemata produces buds which grows into full female or male gametophytes 3. Male gametophytes produces sperm. female gametophyte produces eggs 4. Flagellated sperms swim to eggs 5. Fertilized zygote grows into sporophyte 6. Is nurtured by female gametophyte 7. Mature sporophyte releases spores while still being attached to the female gametophyte

Question 28

How does the moss life cycle depend on water

Answer 28

- Fertilization depends on water since sperms need to swim through the water to reach the egg - Absence of vascular tissue: All parts of the moss gametophyte needs to directly absorb water from the environments - Mosses usually grows in humid and moist habitats for these reasons

Question 29

Moss protonemata looks very similar to

Answer 29

charophyte algae

Question 30

Ferns and differentiated organs

Answer 30

Roots: Anchors plant to ground while absorbing water and nutrients from soil Leaves: Primary photosynthetic organ with a large surface area Stem: Connect leaves to roots while making the plant taller since taller plants have better exposure to light and chances of dispersing their offspring over longer distance

Question 31

Vascular system of ferns

Answer 31

Vascular structure allows nutrient transportation in plant body Xylem: Transport water and minerals - xylem cells are dead at functional maturity - Cell walls strengthened by lignin to provide mechanical strength Pholoem: Transport sugars through the body

Question 32

Ferns no longer need

Answer 32

all parts of its body to absorb water directly from the environment - Leaves can stay dry while they receive water via the vascular system

Question 33

Sporophyll vs sporangia

Answer 33

Sporophyll: Leaves of vascular plants which have been modified to produce spores Sporangium: Reproductive tissue located on the sporophyll which actually produces the spores

Question 34

Explain the process of fern life cycle

Answer 34

1. Spores grows into a bisexual gametophyte 2. Gametophyte produces both the sperm producing organ and the egg producing organ. Sperm swims through moisture to reach the egg 3. Fertilization of egg by sperm to produce the zygote 4. Zygote develops into a sporophyte while it is supported by the gametophyte 5. Mature sporophyte is independent from parental gametophyte. It produces spores from sporangia

Question 35

Ferm gametophyte is much smaller than

Answer 35

the sporophyte - Fern sporophytes do not require complete "wetness" to acquire water for photosynthesis however fern gametophytes still depend on water for fertilization

Question 36

Fern sperms

Answer 36

swim to the egg for fertilization