PLANTS, FUNGI, AND THE COLONIZATION OF LAND
I.
What is a plant?
a. Plants are multi-cellular eukaryotes that make organic
molecules by photosynthesis
i. This definition also fits algae; the major difference is the
adaptations developed for living on land
b. 3 organs
i. Roots
ii. Stems
iii. Leaves
c. CUTICLE  waxy covering to prevent water loss
d. STOMATA  tiny pores on leaf surface to allow for gas
exchange
e. VASCULAR TISSUE  a network of cells joined into narrow
tubes that extend throughout the plant body
i. TWO TYPES
1. XYLEM  transport water and minerals
2. PHLOEM  distribute sugar
f. Reproduction is also a very different process in land plants
from their aquatic ancestors
i. Rely on wind or animals to disperse offspring (or
gametes)
II.
Plants evolved from green algae called charophyceans
a. Aquatic organism that had an adaptation that allowed it to
survive occasional drought
b. Early environment was conducive to plants; lots of sunlight, no
immediate predators (plant-eaters)
III.
Plant diversity provides clues to the evolutionary history of the
plant kingdom
a. BRYOPHYTES  group that includes the mosses; has cuticle
and similar reproduction but no vascular tissue and limited
structural support
b. VASCULAR PLANTS  other ancient lineage of plants;
contain vascular tissue
i. 2 TYPES
1. SEEDLESS PLANTS
2. SEED PLANTS
ii. SEED  consists of an embryo packaged within a food
supply within a protective covering
iii. SPORE  a haploid cell that can develop into a haploid
multi-cellular adult without fusing with another cell
c. Seed plants account for about 90% of the known living plant
species today
d. Seeds are well adapted to land-life; don’t require water for
fertilization (pollination)
i. GYMNOSPERMS  naked seeds
ii. ANGIOSPERMS  flowering plants; seeds created in
specialized structures
IV.
Haploid and diploid generations alternate in plant life cycles
a. ALTERNATION OF GENERATIONS  diploid individuals
called sporophytes and haploid individuals called gametophytes
generate each other in the life cycle
V.
Mosses have a dominant gametophyte
VI.
Ferns, like most plants, have a dominant sporophyte
VII. Seedless plants formed vast “coal forests”
a. FOSSIL FUELS  fuels formed from the remains of ancient
organisms
b. CONIFERS  naked-seed plants that produce cones
VIII. A pine tree is a sporophyte with tiny gametophytes in its cones
a. Pine trees have two types of cones
i. Female cone is hand and woody; contains ovules; the one
we usually see
ii. Male cone is much smaller; softer and short-lived
1. POLLEN GRAINS  male gametophytes
IX.
The flower is the centerpiece of angiosperm reproduction
a. SEPAL  enclose the flower before it opens
b. PETALS  most striking part of flower; important in attracting
insects and other pollinators
c. STAMEN  stalk bearing the anther
d. ANTHER  male organ in which pollen grains develop
e. CARPEL  stalk which contains an ovary at the base and
stigma at the tip
f. STIGMA  traps pollen
g. OVARY  protective chamber for ovules, where eggs develop
X.
The angiosperm plant is a sporophyte with gametophytes in its
flowers
XI.
The structure of a fruit reflects its function in seed dispersal
a. FRUIT  the ripened ovary of a flower
i. Attractive to an animal; seed is not digested and is passed
out of animal in a new location different from where the
fruit was consumed
XII. Agriculture is based almost entirely on angiosperms
a. Flowering plants provide nearly all our food
XIII. Interactions with animals have profoundly influenced angiosperm
evolution
a. The traits of flowering plants vary with the organisms with
which they have a relationship
XIV. Plant diversity is a non-renewable resource
a. 25% of prescription drugs are extracted from plants
b. Only investigated 5,000 of 320,000 plant species as sources of
medicine
c. The exploding population is destroying plant diversity; causing
the extinction of multiple species at once; lowering biodiversity
XV. Fungi and plants moved onto land together
a. Fungi are heterotrophic, so they had to wait for plants to stock
soil with nutrients before they could colonize land
b. Fungi can be parasitic, predatory, or saprophytic (decomposers)
i. Decomposers are essential to recycling dead organisms
XVI. Fungi absorb food after digesting it outside their bodies
a. Heterotrophic organisms that secrete enzymes that digest food
externally and then absorb the nutrients
b. Cell walls made from chitin
c. Non-motile; rooted in ground  only thing in common with
plants
XVII. Many fungi have three distinct phases in their life cycle
XVIII. Lichens consist of fungi living mutualistically with
photosynthetic organisms
a. LICHENS  associations of millions of green algae or
cyanobacteria held in a tangled network of fungal hyphae
i. Still not fully understood
ii. Possible for lichens to survive in habitats that would be
inhospitable to either organism alone
iii. Able to live where there is little or no soil
iv. PIONEER ORGANISMS
1. No soil; but grow in crevices of rocks and increase
rate of erosion and formation of soil for new
species to inhabit
XIX. Parasitic fungi harm plants and animals
a. Most parasitic fungi attack plants (DUTCH ELM DISEASE)
b. Only about 50 are known to be parasitic in humans and other
animals
XX. Fungi have an enormous ecological and practical impact
a. Rely on them as decomposers
b. Used as food
c. Yeast is used in food, as well
d. Used for production of some antibiotics