Unit 1: The Development and Diversity of Plants
1. What is a plant?
a. The plant kingdom includes mosses, ferns, cone baring plants, and flowering plants
b. All plants:
i. Multicellular
ii. Eucariotic (cells have a nucleolus)
iii. Reproduce sexually (uses sperm and egg)
iv. All plants undergo alteration of generations
1. During a plants life cycle it switches from a phase where it produces spores or seeds to a
phase where it produces sperm and egg (gamits)
a. Sporophyte – the spore and seed producing phase of a plants life cycle
b. Gametophyte – the gamete (sperm and egg) producing phase of a plants life
cycle
2. Alteration of generations – alternating between saprophyte and gametophyte phases
during a plants life cycle
c. Most plants:
i. Are photosynthetic
1. There are some parasitic plants that are not photosynthetic. They get food by stealing it
from other plants
2. Photosynthisus - the ability to use light carbon dioxide and water to make glucose
(food)
3. The general chemical formula for photosynthesis is:
6CO2 + 6H2O  C6H12O6 + 6O2
4. Plants absorb all the starting reactants fro photosynthesis through their leaves
5. The light energy plants need to photosynthesize is absorbed through pigments in the
leaves
a. Pigments – molecules that absorb certain colors of light
i. Chlorophyll – the most abundant pigment in plants, that absorbs blue
and red light.
ii. Chlorophyll absorbs mostly blue and red light and reflects green light
2. Photosynthesis
a. Photosynthesis is actually the combination of 2 different reactions, the light reaction, and the dark
reaction
i. Light reaction - converts light energy to molecules that store energy (ATP and NADPH)
1. This reaction takes in water and releases oxygen and hydrogen
ii. Dark reaction - Use the ATP and NADPH made in the light reaction to make carbohydrates like
glucose and starch
1. This reaction rewires Carbon dioxide and the hydrogen released from the light reaction
and releases Carbohydrates
3. How are plants organized
a. There are 3 levels of organization in all organisms including plants
i. Cells - the smallest unit of living things.
ii. Tissue - A group of similar cells working together to perform a function.
iii. Organ - A group of tissues working together to perform a function.
4. Plant cells
a. Plant cells are the same as animal cells except for 3 organelles
i. Vacuoles- large organelles that store water and nutrients
ii. Chloroplasts – organelles that contain chlorophyll and perform photosynthesis
iii. Cell walls – thick Organelle that surrounds the cell membrane and protect the plant cell
5. What are plant organs?
a. All plants have three basic organs:
i. Roots – plant organs that absorbed and store water and nutrients
ii. Stems – plant organs that support the leaves holding them upright to the sunlight
1. There are two types of stems
a. Woody stems
b. Herbacious stems
iii. Leaves – plant organs that absorb light for photosynthesis
6. Each of the 3 organs of the plant is made up of three main types of tissue.
i. Dermal Tissue – the outermost layer of tissue in a plant organ
1. Dermal tissue acts like the skin of the plant
ii. Vascular Tissue – the tissue that circulates water and nutrients through the plant
1. There are two type of vascular tissue:
a. Xylem – circulates water through the plant
b. Phylem – circulates nutrients through the plant
iii. Ground Tissue – the “filler tissue” in between the vascular and dermal tissue in plant organs
1. The ground tissue changes its function depending on what plant organ it is in
b. Plant growth only happens in the roots and steams and originates from a 4th type of tissue
i. Meristem tissue – the tissue that undergoes the most mitoses and allows the plant to grow
7. Anatomy of roots
a. Root hairs – dermal tissue in roots
i. Root hairs absorb water and nutrients from the ground using passive and active transport
1. Passive transport – anything moving from higher concentration to low concentration
without using energy
a. Diffusion (the movement of gasses from high to low) and osmosis (the movement of
water from high to low) are examples of passive transport
2. Active transport – using energy to move anything from low concentration to high
concentration
ii. Because there is a higher concentration of nutrients outside root, root hairs must use active
transport to absorb nutrients into roots
1. Nutrients move into the root through active transport, from low concentration (the soil) to
high concentration (the root hair)
iii. After nutrients are actively pumped into the root, water is absorbed without energy because with all
the nutrients in plant roots, water is usually in higher concentration outside the root.
1. water moves into the root through passive transport (osmosis), from high concentration
(the soil) to low concentration (the root hair)
b. Xylem and phloem is the vascular tissue in roots
c. In roots the ground tissue has large vacuoles and thin cell walls
i. Because the roots main function is to absorb and store water and nutrients the ground tissue in
roots has large vacuoles and thin cell walls to help absorb water and nutrients (thin cell walls) and
store water and nutrients (large vacuoles)
8. Anatomy of stems
a. Dermal tissue in stems
i. Plants with woody stems have dermal tissue called bark
1. Cork - a thick layer of dead, water-proof cells for protection, the outermost layer of bark
a. To help protect the bark, woody stems are often covered in cork
ii. Plants with herbaceous stems have a dermal tissue that produces a cuticle
1. Cuticle - a waxy layer of that often covers the outermost surface of a herbaceous plant
stem
a. The both cork and cuticles prevents moisture from escaping the plant and
protect it
b. Xylem and phloem is the vascular tissue in stems
i. Some plant stems need to move water a nutrients over a long distance
ii. It takes three separate forces to move water from the roots to the leaves of plants
1. Root pressure – pressure created from the water moving into the root.
a. Root pressure alone does not exert enough force to lift water up into trees
2. Capillary Action – waters ability to climb up thin tubes.
a. Since Xylem cells are just really thin tubes this is another possible explanation for
how water can be transferred over a great distance
b. Even the thinnest tubes can only cause water to climb a few cm.
3. Transpiration – the loss of water through leaves
a. As water is lost in the leaves it pulls the water up from the roots to replace it.
b. Transpiration is the strongest force in water transport and thus it plays the largest
role in explaining how water can get all the way up the plant
c. In stems the ground tissue has this cell walls that provide support and flexibility to the plant
i. Because the stems main function is support the leaves, the ground tissue in stems has thick flexible
cell walls to help support the plants leaves but resist snapping in strong wind
9. Anatomy of leaves
a. Dermal tissue in leaves
i. The top and bottom of the leaf are covered with different dermal tissue
ii. The top the leaf is covered in dermal tissue is that produces a cuticle
iii. The bottom of the leaf is covered with dermal tissue that helps absorb the gases and water
needed for photosynthesis
1. Stomata – holes in the underside of a leaf that allow CO2 in and O2 water out of the leaves
a. The loss of water out of the stomata drives transpiration
2. To keep too much water moving into and out of the plant the stomata can’t stay open
a. Guard Cells – Dermal tissue on the underside of the leaf that surround the stomata
and control their opening and closing.
i. Guard cells close the stomata when the plant wilts to conserve water and
open the stomata when there is enough water
b. Xylem and phloem is the vascular tissue in the leaf
c. In leaves the ground tissue has lots or chloroplasts that help the plant photosynthesize
i. Because the leaves main function is photosynthesis, the ground tissue in leaves has lots of
chloroplasts to help the plant photosynthesize
10. Different plants
a. Botanist divide plants into groups base on three characteristics:
i. If the plant contains vascular tissue (xylem and phloem)
ii. If the plant produces spores
iii. If the plant produces seeds in fruits (flowers) or seeds in cones
b. There are 4 main families of plants
i. Mosses – plants that have no vascular tissue and produce spores
ii. Ferns- plants that have vascular tissue and produce spores
iii. Cone Plants- plants that have vascular tissue, and produce seeds in cones
iv. Flowering Plants- plants that have vascular tissue, and produces seeds in fruits (flowers)
11. Evolution of plants
a. Plants evolved from green algae and where some of the first organisms to live completely outside the
ocean about 400 million years ago.
b. Plants had to develop a number of structures to help them survive out of water:
i. Dermal and vascular tissues to prevent them from dehydrating out of water
ii. Structural components to help hold them upright in the air
iii. Ways to allow sperm to reach the egg cells without water
c. The first true plants to develop from algae where mosses
12. Evolution of plants: Bryophytes
a. Bryophytes –mosses, all bryophytes have no vascular tissue and produce spores
i. Bryophytes (mosses) don’t have roots, stems and leaves like most other plants
ii. Bryophytes are short because they all lack vascular tissue
iii. Bryophytes need water for reproduction so the sperm can swim to the egg.
13. Evolution of plants: Ferns
a. Ferns - plants that have vascular tissue and produce spores
i. Bryophytes evolved into ferns by developing vascular tissue.
1. Vascular tissues allowed ferns to grow much taller than their moss predecessors
ii. Ferns where the first plants to develop true roots stems and leaves
iii. Like bryophytes ferns still need water to reproduce
14. Evolution of plants: Gymnosperms
a. Gymnosperms – cone plants, all gymnosperms have vascular tissue, and produce seeds in cones
i. Gymnosperms evolved from ferns by developing the first seeds.
1. Seeds are more evolved than spores because it has a protective coat and a supply of
food that can keep the embryo inside alive for a long time
ii. Gymnosperm literally means “Naked Seed” because the seeds are exposed in cones
iii. The most recognizable group of gymnosperms are conifers
iv. Gymnosperms produce pollen which gives the plant the ability to reproduce without water
v. Conifers – the group of gymnosperms that include pine trees
1. conifers produce stems made out of “soft wood”
2. The resin that makes conifers smell “piney” is a adaptation that is antibacterial,
antifungal, and helps stop insect attacks
15. Evolution of plants: Angiosperms
a. Angiosperms – flowering plants, all angiosperms have vascular tissue and produce seeds in flowers
i. Angiosperms evolved from gymnosperms by developing fruits that help spread their seeds
ii. All the fruit that is consumed was produces by some type of angiosperm
iii. Angiosperms produce pollen which gives the plant the ability to reproduce without water
iv. Angiosperms have become the most diverse phyla of plants, and so botanists have developed
ways of classifying them
1. Monocots vs. Dicots (based on the seed that the flowering plant produces)
a. Monocots produce seeds with 1 cotyledons
i. Monocot leaves have parallel vanes
ii. Monocot flowers have parts in multiples of 3
iii. The xylem and phloem in monocot stems is scattered throughout the
stem
iv. monocot roots are fibrous
b. Dicots produce seeds with 2 cotyledons
i. Dicots leaves have branched vanes
ii. Dicots flowers have parts in multiples of 4 or 5
iii. The xylem and phloem in Dicot stems is arranged in a ring
iv. Dicots have a tap root (like a carrot)