Lecture 15

Question 1

characteristics of most land plants.

Answer 1

Multicellular, eukaryotic
Cellulose in cell wall
Store excess glucose as starch

Form embryos

Most Terrestrial (sea grasses are aquatic)
Most have roots, stems, leaves (algae don’t have)
Autotrophic: (almost all) produce own organic compounds

Have adaptations that allow for survival & reproduction on land

Question 2

Define the term producer.

Answer 2

Plants are producers. They make their own food, which creates energy for them to grow, reproduce and survive.

Question 3

List challenges to living on land and how plants faced them.

Answer 3

Challenge:
Water loss = Plant body, gametes, & embryos can dry out (desiccation)
(waxy cuticle & reproductive adaptations)

Gas exchange = Reduced due to waxy cuticle. (Stomata)

Structural support = Gravity may cause collapsing (lignin in vascular tissue)

Reproduction = Fertilization: Little water for swimming gametes (some swim, others float thru air or transported by pollinators).

Question 4

some adaptations to specific land conditions.

Answer 4

Plant Adaptations to Hot/Dry Climates
To limit water loss:
thick cuticle, fewer stomata, opening stomata only at night to gather and store CO2

To store water:
Enlarged stems for water storage (ex. cacti)
Thicker leaves for water storage (ex. aloe)
To take up water:
Deep root systems
Shallow laterally extensive root systems

Plant Adaptations to Wet Climates
Thin cuticle (if any)
Air sacs and large flat leaves for flotation
Increased number of stomata

Plants in the cold
Conical shape & flexible branches shed snow.

Evergreen: more time for photosynthesis*

Question 5

Almost* all plants have these (vegetative) organs

Answer 5

Roots: Anchor plants, nutrient uptake & storage

Stems: ↑ height of plants & ↑ exposure to light
Transport of nutrients
Support for leaves, flowers, fruits

Leaves: Site of photosynthesis
↑ surface area exposed to light: ↑ photosynthesis

Question 6

4 types of plants

Answer 6

1. Nonvascular: bryophytes
   Photosynthetic, (some have waxy cuticle & stomata) BUT:

No vascular system:
get water & nutrients by cell-to-cell diffusion
Small compact, slow growing

Generally live in moist environments b/c they need water for reproduction

2. Ferns
   VASCULAR TISSUE: absorb & distribute water & nutrients to leaves meters away
   Can grow BIGGER
   Sperm must “swim” to eggs (like bryophytes)
3. Gymnosperms:
   Gametes protected in pollen grains & ovules
   Reproduce by forming seeds
   Seeds exposed on a stem or in a cone
4. Angiosperms: Flowering plants
   Gametes protected in pollen grains & ovules
   Reproduce by forming seeds
   Seeds enclosed/protected in an ovary→ fruit

Question 7

Advantages to having seeds

Answer 7

Seed coat protects embryo from desiccation & from getting crushed.

Seeds contain an abundant food supply for the embryo: embryo can develop (see #3)

Embryonic development is very advanced before the seed germinates & the plant is exposed to the environment. Compare with moss & ferns: embryos never protected

Mechanisms for seed dispersal ensure that the embryo will grow away from parent plant to reduce competition with the parent