Plant Diversity presentation (1).pdf biology

Plant diversity

2. •Land plants evolved from a group of green
algae, perhaps as early as 510 million
years ago.
•Plants make our lives possible. Without the
glucose they create through photosynthesis,
and the oxygen they release into the air, it
would be impossible for human life to
continue on.

3. •The Paleozoic era is divided into six periods:
Cambrian → Ordovician → Silurian → Devonian →
Carboniferous → Permian
•More than 500 million years ago, land plants first appeared in
the Ordovician.
•Fossilized plant cells, cuticles, and spores date back to the
Ordovician.
•Oldest known vascular plants appeared in the Devonian.
•The Rhynie chert (Scotland) contains well-preserved early
vascular plant fossils.

5. Introduction to Green Algae:
•Green algae belong to the group Streptophyta, which includes both green algae
and land plants.
•They share key traits like carotenoids and chlorophyll a and b, similar to land
plants.
•Store carbohydrates as starch and divide cells using phragmoplasts
Types of Green Algae:
•Chlorophyta: Over 7,000 species found in different environments like freshwater,
seawater, and even snow.
Examples of species:
⚬Spirogyra: Forms chains of cells.
⚬Desmids: Single-celled, oval-shaped cells.
⚬Chlamydomonas: Single-celled with flagella.
⚬Ulva: Colony-forming algae resembling leaf lettuce.

6. Charales – Close Relatives to Land Plants
• *Chara* (muskgrass/skunkweed) is a representative of *Charales*, a group of
green algae.
•These algae produce *lignin* and *sporopollenin*, compounds also found in land
plants.
•They have *plasmodesmata* and flagellated sperm.
•Do *not* exhibit alternation of generations.
•Recent DNA studies suggest *Zygnematales* (including Spirogyra) might be even
closer to land plants than Charales.

8. •Bryophytes reproduce via spores and depend
on water for fertilization.
•It contains three groups of non-vascular land
plants: the liverworts, hornworts, and
mosses.
•It does not have xylem
and phloem.
•It absorbs water and
nutrients directly through
their surface.

9. •Gametophyte – photosynthetic stage of bryophytes that produces gametes.
•Sporophyte – dependent stage that grows on the gametophyte and
produces spores for reproduction.
•Protonema – The early growth stage of mosses, appearing as a thin, thread-
like structure from which mature mosses develop.
•Antheridia – Male reproductive organs that produce and release sperm
cells.
•Archegonia – Female reproductive organs that produce eggs and where
fertilization occurs.
•Rhizoids – Hair-like structures that anchor the plant to the substrate and
help absorb water but are not true roots.
•Spores – Tiny, haploid reproductive cells that disperse and grow into new
gametophytes when conditions are favorable.

10. •The name “liverworts” is derived from the belief in
ancient times that the diseases of the liver could be
cured with these plants.
•Liverworts are part of the kingdom Plantae, in the
division Marchantiophyta. While the plants are small,
and often overlooked, liverworts can be found globally,
wherever plants can grow.

11. --->Thallose Liverwort - Liverworts with
broad, flat, lobed bodies, resembling a
green ribbon or leafy mat.
--->Leafy Liverwort - Liverworts with
small, thin, overlapping leaf-like
structures.

12. •The common name refers to the
elongated horn-like structure,
which is the sporophyte.
•Hornworts may be found
worldwide, though they tend to
grow only in places that are damp
or humid.
•Single chloroplast per cell

13. •Mosses are distributed throughout the
world except in salt water and are
commonly found in moist shady
locations.
•They are best known for those
species that carpet woodland and
forest floors.
•Seta – The stalk that connects the
capsule to the gametophyte.
•Capsule – A spore-producing
structure at the tip of the sporophyte.
•Peristome teeth – Tiny, tooth-like
structures inside the capsule that help
control when and how spores are
released.

17. •300 million years ago, seedless plants dominated the landscape and grew in the
enormous swampy forests of the Carboniferous period. Their decomposition created
large deposits of coal that we mine today.
Seedless plants are any plants with vascular tissue that do not produce seeds. As these
plants do not use seeds to reproduce they do not produce any flowers.
•The evolutionary transition from water to land imposed severe constraints on plants.
They had to develop strategies to avoid drying out, to disperse reproductive cells in
air, for structural support, and for capturing and filtering sunlight.
• Most seedless plants still require a moist environment.

18. Seedless vascular plants are a group of plants that have vascular tissues
(xylem and phloem) but do not produce seeds. Instead, they reproduce via
spores and require water for fertilization. This group includes ferns, horsetails,
club mosses, and whisk ferns. They played a crucial role in the Carboniferous
Period, forming coal deposits that later became fossil fuels.

19. 1. Vascular Tissue: Transport and
Structural Support
•Xylem
•Phloem
2. True Roots: Structural Support
and Nutrient Absorption
•Rhizomes
•Adventitious roots
3. Leaves and Stems
•Microphylls
•Megaphylls
1. Alternation of Generations
•Sporophyte
•Gametophyte
2. Spore Production and
Dispersal
3. Gametophyte and Fertilization
4. Homospory vs. Heterospory
•Homosporous plants
•Heterosporous plants
- Microspores (male)
- Megaspores (female)

20. 1. Division Lycopodiophyta
•Lycopodium (Club Mosses)
•Selaginella (Spike Mosses)
•Isoetes (Quillworts)
2. Division Pteridophyta
•Pteridophyta (Ferns)
•Equisetophyta (Horsetails)
•Psilotophyta (Whisk Ferns)
1.Ecological Role
2.Historical & Economic
Significance
3. Medicinal & Practical
Uses
4. Environmental Indicators

23. Term Definition
Sporophyte (2n)
Dominant diploid
phase; produces
spores.
Gametophyte (n)
Haploid phase that
produces gametes.
Sporangia
Structures where
spores are formed
via meiosis.
Sori
Clusters of sporangia
found on fern fronds.
Prothallus
Small, heart-shaped
gametophyte stage.
Antheridia
Male reproductive organs
producing sperm.
Archegonia
Female reproductive organs
containing eggs.
Tracheids
Water-conducting cells in the
xylem.
Lignin
Strengthens plant cell walls
and vascular tissues.
Homosporous
Producing only one type of
spore.
Heterosporous
Producing two types of spores
(microspores and
megaspores).

25. KEY FEATURES OF SEED
PLANTS
•SEED PRODUCTION
•VASCULAR TISSUE
•POLLINATION & FERTILIZATION
•HETEROSPORY
•DOMINANT SPOROPHYTE STAGE
•ADAPTATIONS FOR LAND
TWO MAJOR GROUPS OF
SEED PLANTS
•GYMNOSPERMS
•ANGIOSPERMS
IMPORTANCE OF SEED PLANTS
•FOOD SOURCE
•OXYGEN & CARBON CYCLE
•ECOSYSTEM STABILITY
•MEDICINAL & ECONOMIC VALUE

26. Seed plants are the most successful and diverse group of plants on Earth today.
Their evolution was a major advancement in plant history, allowing them to
dominate various ecosystems by overcoming the limitations of seedless
vascular plants. The ability to produce seeds and pollen freed seed plants from
relying on water for fertilization, enabling them to thrive in drier environments.

27. a.) Evolution of Seed Plants: Major Adaptations
1. Seeds: Protection & Dormancy
•Seeds contain an embryo, a food supply, and a protective seed coat,
allowing them to survive harsh conditions.
•Unlike spores, seeds can remain dormant until conditions are favorable for
germination.
2. Pollen: Water-Free Fertilization
•Unlike ferns and mosses, which rely on water for sperm movement, seed
plants evolved pollen grains.
•Pollen contains sperm and is transported by wind, insects, or animals,
enabling reproduction in dry environments.

28. 3. Heterospory: Specialized Male & Female Gametophytes
•Seed plants developed heterospory, meaning they produce two types of spores:
Microspores → Develop into pollen grains (male gametophytes).
•Megaspores → Develop into ovules (female gametophytes).
•This adaptation ensures a higher chance of fertilization and genetic diversity.
4. Reduction of the Gametophyte Generation
•In seed plants, the sporophyte (diploid) stage is dominant, while the gametophyte
(haploid) stage is greatly reduced.
•The female gametophyte develops inside the ovule, protected within the parent plant.
5. Vascular Tissue & Secondary Growth
•Advanced xylem (with tracheids and vessel elements) and phloem allow efficient water
and nutrient transport.
•The evolution of vascular cambium led to wood formation, enabling plants to grow
larger and live longer.

29. Origin and Early Evolution
•Gymnosperms evolved from progymnosperms, an extinct group of seedless vascular
plants with woody tissues.
•They first appeared in the Carboniferous Period (~319 million years ago) and became
dominant during the Mesozoic Era ("Age of Gymnosperms").
Gymnosperm Adaptations
1. Naked Seeds – Unlike angiosperms, gymnosperm seeds are not enclosed within fruits
but develop on cone scales.
2. Wind Pollination – Gymnosperms primarily rely on wind to transport pollen to female
cones.
3. Needle-Like Leaves – Many gymnosperms, such as conifers, have small, waxy leaves
that reduce water loss.
4. Deep Roots – Enabled survival in nutrient-poor soils and cold climates.
b.) Evolution of Gymnosperms

30. Major Groups of Gymnosperms
1. Cycads (Cycadophyta) – Palm-like plants that were abundant during the Mesozoic.
2. Ginkgo (Ginkgophyta) – Only one surviving species (Ginkgo biloba), considered a
"living fossil."
3. Conifers (Pinophyta) – Largest group, includes pines, firs, redwoods, and cedars.
4. Gnetophytes (Gnetophyta) – Unique gymnosperms, including Ephedra, Gnetum,
and Welwitschia.
Decline of Gymnosperms
Gymnosperms began to decline in the Cretaceous Period (~145-66 million years ago)
as angiosperms evolved and diversified, outcompeting gymnosperms in many
ecosystems.
b.) Evolution of Gymnosperms

31. Origin and Early Evolution
•Angiosperms evolved around 140-125 million years ago during the Early
Cretaceous Period.
•They quickly diversified and became the dominant plant group by the Late
Cretaceous (~66 million years ago).
•Fossil evidence suggests that early angiosperms evolved from gymnosperm-
like ancestors, possibly related to Bennettitales, an extinct order of seed
plants.
c.) Evolution of Angiosperms

32. Angiosperms Adaptation
1. Flowers: Specialized Reproductive Structures
•Flowers evolved to attract pollinators (insects, birds, mammals),
increasing fertilization success.
•This led to coevolution between plants and pollinators.
2. Enclosed Seeds & Fruits
•Unlike gymnosperms, angiosperms enclose their seeds within fruits.
•Fruits aid in seed dispersal by wind, water, or animals.
3. More Efficient Vascular System
•Vessel elements in the xylem allow faster water transport than
gymnosperm tracheids.
•Improved phloem structure enables better nutrient distribution.
c.) Evolution of Angiosperms

33. 4. Double Fertilization
•Unique to angiosperms, forming both:
•Embryo (2n) → Grows into a new plant.
•Endosperm (3n) → Provides nourishment to the developing seed.
5. Rapid Growth & Life Cycles
•Angiosperms grow and reproduce faster than gymnosperms, outcompeting
them.
c.) Evolution of Angiosperms

34. Major Groups of Angiosperms
1. Monocots – One cotyledon, parallel veins, fibrous roots (e.g., grasses, lilies,
palms).
2. Dicots (Eudicots) – Two cotyledons, branching veins, taproots (e.g., roses, oak
trees, sunflowers).
Angiosperm Success and Global Dominance
•Coevolution with Pollinators – Many angiosperms evolved alongside bees,
butterflies, birds, leading to specialized pollination strategies.
•Diverse Habitats – Angiosperms adapted to forests, grasslands, deserts, and
aquatic environments.
•·Agricultural Importance – Most human food comes from angiosperms (wheat,
rice, fruits, vegetables, spices).
c.) Evolution of Angiosperms

35. •From the Greek word Gymno or gymnos means "naked", while sperm means
"seeds".
•First plant to have a seeds.
•Gymnosperms are a group of plants that produce seeds exposed on cones,
rather than enclosed in fruits.
•Ex. pine trees, spruce trees, fir trees, cedar trees, and cycads.

38. •A group of plants that produce seeds enclosed within a fruit.
•They are characterized by their flowers, which facilitate
reproduction through pollination
•Ex: roses, sunflowers, apples, and oak trees.

39. - The reproductive organ of
angiosperms.
- All flowers contain the same
structures: sepals, petals, carpels, and
stamens.
- Contains male (stamens) and female
(pistils) parts.
- Flowers attract pollinators to enable
fertilization.

40. - Fruits in angiosperms are mature
ovaries of flowers containing seeds.
- They develop after fertilization and
help in seed protection and dispersal.
- Fruits can be classified as fleshy and
dry
- The fruit structure and characteristics
vary widely among species.

43. •Coevolution of flowering plants and insects - both diversified
in the Mesozoic.
•Herbivory and pollination drive plant and insect diversity.
•Plants develop defenses against herbivores: alkaloids in
seeds, bark, spines, and thorns.
•Herbivores adapt with specialized mouthparts or beaks.
•Mutualism: plants offer food to animals in exchange for seed
dispersal.
•Ex: acacia trees provide shelter/food for ants, ants protect
trees from herbivores

44. •Wind Pollination: Grasses and large trees like oaks, maples, and birches rely on wind to
distribute pollen. Their flowers are small and lightweight.
•Animal Pollination: Over 80% of angiosperms depend on animals for pollination, which
involves transferring pollen between flowers.
•Floral Adaptations: Plants have developed unique traits (e.g., nectar secretion) to attract
specific pollinators like insects and birds.
•.Pollinator-Specific Flowers:
- Bees & Butterflies: Flowers with UV patterns.
- Hummingbirds: Large, red, funnel-shaped flowers.
- Moths: White, nocturnal flowers.
- Other Pollinators: Bats, lemurs, and lizards.
•Consequences of Disruption: Loss of pollinators (e.g., bee population decline) can severely
affect crops and agriculture.

45. 1. Seed Plants as foods:
- Staple Crops: Rice, wheat, and potatoes are the foundation of many diets.
- Nutrients: Beans, nuts (proteins), fruits, and vegetables (vitamins, fiber).
- Sugar & Drinks: Sugar from sugarcane, beverages from tea, coffee, and
cocoa beans.
2. Alcohol Production:
- Alcoholic beverages like wine and beer come from fermented plant sugars.
3. Non-Food Uses:
- Timber and Paper: Wood for construction and paper from conifers.
- Textiles: Cotton, flax, and hemp for fabric.
- Dyes & Perfumes: Plant-derived dyes (indigo) and fragrances.
4. Medicinal Uses:
- Ancient healing uses; modern drugs (e.g., morphine, aspirin) are derived
from plants.
5. Cultural Significance:
- Ornamental plants for beauty and inspiration in art and poetry.

46. Importance:
- Provides food, medicine, and oxygen.
- Balances ecosystems, protects
watersheds, moderates climate.
- Shelters diverse animal species.
Threats:
- Human population growth and
deforestation.
- Economic development and pollution.
- Poaching for valuable woods (e.g.,
Ebony, Rosewood).
Conservation:
- Protected areas (parks, reserves).
- Sustainable practices in
agriculture/forestry.
- Preserving heirloom seeds and
barcoding species.
Urgency:
- Immediate action needed to prevent
irreversible ecosystem damage and
biodiversity loss.