20.
3 Diversity of Flowering Plants
KEY CONCEPT
The largest phylum in the plant kingdom is the
flowering plants.
20.3 Diversity of Flowering Plants
Flowering plants have unique adaptations that allow them
to dominate in today’s world.
• Flowers allow for efficient pollination.
– animals feed on pollen or nectar
– pollen is spread from flower to flower in a very
targeted way. For this reason, flowering plants
pollinated by animals don’t need to produce
nearly as much pollen as do plants that rely on
the wind to randomly transfer their pollen.
20.3 Diversity of Flowering Plants
Explain why animal pollination is more efficient than wind
pollination.
Wind pollination is less targeted; pollen grains land
wherever the wind takes them. Animal pollinators, on the
other hand, often move from flower to flower while they are
feeding.
20.3 Diversity of Flowering Plants
• Fruit allows for efficient seed dispersal.
Fruit is flower’s ripened ovary.
Fruits protect the seeds of flowering plants and
often play a role in seed dispersal.
Many forms, each function in seed dispersal.
20.3 Diversity of Flowering Plants
Botanists classify flowering plants into two groups based
on seed type.
• A cotyledon is an embryonic “seed leaf.”
• Monocots have a single seed leaf.
– leaf veins usually parallel
– flower parts usually in multiples of 3
– bundles of vascular tissue scattered in stem
20.3 Diversity of Flowering Plants
• Dicots have two seed leaves.
– leaf veins usually netlike
– flower parts usually in multiples of 4 or 5
– bundles of vascular tissue in rings in stem
20.3 Diversity of Flowering Plants
20.3 Diversity of Flowering Plants
Warm up:
Differentiate between the 2 types of stems
20.3 Diversity of Flowering Plants
20.3 Diversity of Flowering Plants
Flowering plants are also categorized by stem type and
lifespan.
• Stem type can be woody or herbaceous.
– Wood is a fibrous
material made up of
dead cells.
– Wood has high
concentrations of
lignin and cellulose.
– Woody stems
are stiff.
Oak
– Plants that do not produce wood, such as cucumbers,
cacti, and marigolds, are called herbaceous plants.
20.3 Diversity of Flowering Plants
Flowering plants are also categorized by stem type and
lifespan.
Herbaceous plants do not produce wood.
Iris
20.3 Diversity of Flowering Plants
• There are three types of plant life spans.
– Annuals mature from seed,
flower, and die in one year.
– Corn and lettuce are
common annuals, as are
some garden flowers such
as zinnias
Wheat
20.3 Diversity of Flowering Plants
• There are three types of plant life spans.
– Annuals mature from seed,
flower, and die in one year.
– Biennials take two years to
compete life cycle.
Carrots are common
biennial garden plants.
Foxglove
20.3 Diversity of Flowering Plants
• There are three types of plant life spans.
– Annuals mature from seed, flower, and die in one year.
– Biennials take two years to compete life cycle.
– Perennials live more than two years.
– Most woody plants, including trees, are perennials.
Big bluestem
20.3 Diversity of Flowering Plants
20.3 Diversity of Flowering Plants
Formative assessment p:589
1. What adaptations give flowering plants a reproductive
advantage over gymnosperms?
2. What are the primary differences between monocots and
dicots?
3. Name three ways in which flowering plants can be
categorized.
4. Contrast In what ways does pollination in gymnosperms
differ from pollination in angiosperms?
5. How would you take plant lifespan type into account
when planning a garden?
20.3 Diversity of Flowering Plants
• MASS EXTINCTIONS 6. The fossil record reveals a
mass extinction at the end of the Cretaceous period.
Discuss why mass extinctions are commonly followed by
a period of adaptive radiation, in this case, of flowering
plants
20.3 Diversity of Flowering Plants
1. Animal pollination is more efficient than wind pollination,
flower ovaries protect gametes and seeds, and fruit
protects seeds and helps to disperse them.
2. monocots: one cotyledon per seed; dicots: two
cotyledons per seed
3. by number of cotyledons: monocot or dicot; by stem
type: woody or herbaceous; or by lifespan: annual,
biennial, or perennial.
4. Gymnosperms rely on wind for pollination; angiosperms
are pollinated by wind or animals.
5. Annuals will need to be replanted every year. Biennial
plants will not flower the first year if planted from seed,
and they will need to be replanted after their second year
of growth. Perennial plants will grow back every spring.
20.3 Diversity of Flowering Plants
• 6. A mass extinction leaves open niches and unused
abiotic resources. Surviving species may be able to
adapt to these niches, expanding their range and
possibly radiating into new species over many
generations.
