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Chapter 26: Phylogeny and the Tree of Life

Phylogenies Show Evolutionary Relationships

1. Define phylogeny and explain how phylogenies are used.

  • Phylogeny: The evolutionary history of a species or group of related species.

  • Use of phylogenies: Helps scientists understand evolutionary relationships and construct phylogenetic trees.

2. Define systematics.

  • Systematics: A branch of biology that classifies organisms and determines their evolutionary relationships.

3. What is binomial nomenclature?

  • A system for naming species using two parts: genus and species.

4. What are the two components of every binomial name?

  • Genus (capitalized)

  • Species (lowercase)

Taxonomy and Classification

5. What are the taxonomic categories in hierarchical order?

  • Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

  • Mnemonic: Dear King Philip Came Over For Good Spaghetti

6. Which organisms are more closely related: those in the same phylum or the same order?

  • Same order → More specific category than phylum.

Understanding Phylogenetic Trees

7. What does a branch point in a phylogenetic tree represent?

  • A common ancestor from which two lineages diverged.

8. Define sister taxa.

  • Sister taxa: Groups that share an immediate common ancestor and are each other's closest relatives.

9. How can a phylogenetic tree be drawn differently while still showing the same information?

  • It can be horizontal, vertical, or diagonal—only the branching pattern matters, not the orientation.

10. In a phylogenetic tree, are humans more closely related to frogs or lizards? Explain.

  • Lizards → Humans and lizards share a more recent common ancestor than humans and frogs.

11. What does it mean for a phylogenetic tree to be rooted?

  • A rooted tree has a branch representing the most recent common ancestor of all taxa in the tree.

12. Why are fishes considered the basal taxon?

  • They are the earliest diverging lineage in a given tree.

13. Three key points about phylogenetic trees that cannot be determined:
a. Actual ages of species
b. Exact amount of genetic change
c. Whether one taxon evolved from another

Inferring Phylogenies from Morphological and Molecular Data

14. How are phylogenetic trees inferred?

  • By analyzing morphological (physical) and molecular (DNA/protein) similarities.

15. Differentiate between homologous and analogous structures.

  • Homologous: Similar due to shared ancestry (e.g., whale fin & bat wing).

  • Analogous: Similar due to convergent evolution (e.g., bird wing & butterfly wing).

16. Why is it important to distinguish homologous from analogous structures?

  • Only homologous traits should be used to infer evolutionary relationships.

17. How can DNA homologies be determined after genetic changes?

  • By aligning gene sequences and identifying conserved regions.

18. If species A and B look alike but have different gene sequences, while species B and C look different but have similar gene sequences, which are more closely related?

  • B and C (genetic similarity is more reliable than appearance).

Constructing Phylogenetic Trees Using Shared Characters

19. What is a clade?

  • A group including an ancestor and all its descendants (monophyletic group).

20. Why is Group I monophyletic?

  • It includes a single ancestor and all its descendants.

21. Why is Group II paraphyletic?

  • It includes an ancestor but not all descendants.

22. Why is Group III polyphyletic?

  • It includes taxa with different ancestors.

23. What is a shared derived character?

  • A new trait that evolved in a clade but not in ancestors.

24. Why is hair a shared derived character for mammals but a backbone is not?

  • Hair evolved in mammals only (derived), while backbones appeared earlier (ancestral).

25. Why is a lancelet considered the outgroup in Figure 26.12?

  • It shares the fewest derived characters with the other taxa.

26. What animals belong to a clade starting with four limbs?

  • Amphibians, reptiles, birds, and mammals.

Using Maximum Parsimony in Evolutionary Biology

27. How does maximum parsimony apply to phylogenetic trees?

  • The simplest explanation (fewest evolutionary changes) is most likely correct.

28. What does a phylogenetic tree represent?

  • A hypothesis about evolutionary relationships.

29. What evidence suggests birds are closely related to crocodiles?

  • DNA, fossil evidence, and shared derived traits (e.g., similar heart structure, nest-building behavior).

Genomic Evidence of Evolutionary History

30. How does a genome help determine evolutionary relationships?

  • DNA sequences reveal genetic similarities and divergence over time.

31. Which method shows fungi are more closely related to animals than plants?

  • rRNA gene comparison (changes slowly over time).

32. Which method reveals Native American ancestry?

  • Mitochondrial DNA (mtDNA) (evolves quickly).

33. What are orthologous genes?

  • Genes in different species from a common ancestor (e.g., human and mouse hemoglobin genes).

34. What are paralogous genes?

  • Genes duplicated within a species that evolve independently (e.g., human hemoglobin genes).

35. Why are mice good model organisms for studying human diseases?

  • They share many homologous genes with humans.

36. What does it mean when genes are conserved?

  • They remain unchanged over time, indicating descent from a common ancestor.

Molecular Clocks and Evolutionary Time

37. What are molecular clocks?

  • Models that estimate the time of evolutionary divergence based on DNA mutations.

38. How do molecular clocks work?

  • Assume mutations accumulate at a constant rate over time.

39. When did HIV emerge according to molecular clocks?

  • Around 1930.

40. Two problems with molecular clocks:
a. Mutation rates are not always constant.

Chapter 29: Plant Diversity I: How Plants Colonized Land

29.1 Key Derived Characters of Plants

  • Plants evolved from green algae (charophytes).

  • Five Key Traits Shared with Green Algae:

    1. Rings of cellulose-synthesizing proteins

    2. Peroxisome enzymes

    3. Structure of flagellated sperm

    4. Formation of a phragmoplast

    5. Sporopollenin (prevents drying out)

  • Sporopollenin: A polymer that protects spores and zygotes from drying out, allowing colonization of land.

  • Alternation of Generations (Life Cycle):

    • Key Events: Fertilization and meiosis

    • Gametophyte (n) → produces gametes via mitosis

    • Sporophyte (2n) → produces spores via meiosis

  • Derived Traits of Plants for Terrestrial Life:

    1. Sporangia: Organs where spores are produced

    2. Spores: Haploid cells that grow into gametophytes

    3. Cuticle: Waxy layer that prevents water loss

    4. Apical meristems: Regions of active growth in roots and shoots

    5. Stomata: Pores for gas exchange

    6. Vascular tissue: Conducts water and nutrients

    7. Seed: A plant embryo with a food supply and protective coat

    8. Gymnosperms: Plants with "naked" seeds (e.g., pine trees)

    9. Angiosperms: Flowering plants with seeds in fruit (e.g., apple trees)

29.2 Life Cycle of Nonvascular Plants (Bryophytes)

  • Dominant Generation: Gametophyte (haploid, n)

  • Reproductive Structures:

    • Antheridium: Produces sperm

    • Archegonium: Produces eggs

  • Sporophyte (2n) produces spores via meiosis

  • Spore Dispersal: By wind or water

  • Fertilization: Requires water; sperm swims to egg

29.3 Seedless Vascular Plants

  • First plants to grow tall due to vascular tissue.

  • Types of Vascular Tissue:

    • Xylem: Transports water and minerals

    • Phloem: Transports sugars and nutrients

  • Competitive Advantage of Vascular Plants:

    • Grow taller → better access to sunlight

    • Structural support from lignin

  • Roots: Absorb water and anchor plants

  • Leaves: Increase surface area for photosynthesis

  • Dominant Generation: Sporophyte (diploid, 2n)

  • Moist Environment Required: Sperm needs water to reach the egg


Chapter 30: Plant Diversity II – The Evolution of Seed Plants

30.1 Seeds and Pollen Grains: Key Adaptations for Land

  • Three Components of a Seed

    1. Embryo – Young developing plant

    2. Food Supply – Provides nutrients

    3. Seed Coat – Protection

  • Five Common Characteristics of Seed Plants

    1. Reduced gametophyte stage

    2. Heterospory (microspores & megaspores)

    3. Ovules

    4. Pollen production

    5. Seeds

  • Why Pollen & Seeds Are Important for Land Adaptation

    • Pollen: Eliminates need for water for fertilization

    • Seeds: Provide protection & nourishment, allow dormancy

  • Advantages of Miniaturized Gametophytes

    1. Protection from environmental stress

    2. Dependent on sporophyte for nutrients

    3. No need for water for fertilization

    4. Enhanced dispersal mechanisms

  • Heterospory (Two Types of Spores & Their Development)

    • Megaspore → Develops into female gametophyte → Produces eggs

    • Microspore → Develops into male gametophyte → Produces sperm

  • Pollination Purpose

    • Transfer of pollen to ovules for fertilization

  • Advantages of Pollen Over Free-Swimming Sperm

    1. No dependence on water

    2. Increased dispersal distance

  • Advantages of Seeds Over Spores

    1. Can remain dormant until favorable conditions

    2. Contain stored food for the embryo

    3. Can be transported long distances

30.2 Gymnosperms: "Naked" Seeds on Cones

  • Four Phyla of Gymnosperms

    1. Cycadophyta (cycads)

    2. Ginkgophyta (Ginkgo biloba)

    3. Gnetophyta (Ephedra, Gnetum, Welwitschia)

    4. Coniferophyta (conifers: pines, firs, spruces)

  • Five Examples of Coniferophyta

    1. Pines

    2. Firs

    3. Spruces

    4. Redwoods

    5. Cedars

  • Gymnosperm Life Cycle (Pine Life Cycle Highlights)

    1. Sporophyte (tree) produces cones

    2. Male cones make pollen; female cones make ovules

    3. Wind pollination transfers pollen

    4. Fertilization occurs inside ovule

    5. Seed forms & disperses

    6. Seed germinates into new sporophyte

  • Why Gymnosperm Seeds Are "Naked"

    • They are not enclosed in fruits (develop on cone scales)

30.3 Angiosperms: Flowers & Fruits

  • What "Covers" Angiosperm Seeds?

    • Fruit (derived from ovary)

  • Function of Flowers

    • Specialized reproductive structures

    • Attract pollinators for fertilization

  • Parts of a Flower & Their Functions

    1. Sepals – Protect bud

    2. Petals – Attract pollinators

    3. Stamens (Anther + Filament) – Male reproductive structures

    4. Carpel (Stigma + Style + Ovary) – Female reproductive structures

  • Botanical Definition of a Fruit

    • Mature ovary that encloses seeds

  • Two Functions of Fruits

    1. Protect seeds

    2. Aid in dispersal

  • Cross-Pollination vs. Self-Pollination

    • Cross-Pollination: Pollen from one plant fertilizes another

    • Self-Pollination: Pollen fertilizes ovules of the same plant

  • Evolutionary Advantage of Cross-Pollination

    • Increases genetic variation

  • Double Fertilization (Two Events Occur)

    1. One sperm fertilizes egg → Forms zygote

    2. One sperm fertilizes central cell → Forms endosperm (food source)

  • Key Results of Double Fertilization

    1. Ovule → Seed

    2. Zygote → Embryo

    3. Endosperm → Nutrient tissue for embryo

  • Differences Between Monocots & Eudicots
    | Characteristic | Monocots | Eudicots |
    |---------------|---------|---------|
    | Cotyledons | 1 | 2 |
    | Leaf veins | Parallel | Net-like |
    | Flower parts | Multiples of 3 | Multiples of 4 or 5 |
    | Stem vascular bundles | Scattered | Arranged in a ring |

30.4 Human Welfare & Seed Plants

  • Importance of Seed Plants to Humans

    • Food: Grains, fruits, vegetables, nuts

    • Wood: Timber, paper, construction

    • Medicines: Many drugs derived from plants (e.g., aspirin from willow bark)

  • Threats to Plant Diversity

    1. Deforestation

    2. Habitat destruction

    3. Climate change

    4. Overharvesting

Test Your Understanding

  1. _________

  2. _________

  3. _________

  4. _________

  5. _________

  • Derived Characters on Phylogenetic Tree:

    • (a) Flowers

    • (b) Embryos

    • (c) Seeds

    • (d) Vascular tissue

Chapter 35: Plant Structure, Growth, and Development

35.1 Plant Structure and Organization

Hierarchy of Plant Body

  1. Organs: Root, Stem, Leaf

  2. Tissues: Dermal, Vascular, Ground

  3. Cells: Parenchyma, Collenchyma, Sclerenchyma, Xylem, Phloem

Roots

  • Functions: Anchorage, Water/Nutrient Absorption, Storage

  • Types:

    • Taproot System: One main root, deep soil penetration (e.g., dicots)

    • Fibrous Root System: Many small roots, prevents erosion (e.g., monocots)

  • Root Hairs: Increase surface area for absorption

Stems

  • Function: Support, Transport, Storage

  • Nodes: Points where leaves attach

  • Internodes: Stem segments between nodes

  • Buds:

    • Apical Buds: Primary growth (length)

    • Axillary Buds: Potential for new branches

Specialized Stems:

  1. Rhizomes – underground stems (e.g., ginger)

  2. Tubers – storage stems (e.g., potato)

  3. Stolons – horizontal stems (e.g., strawberries)

Leaves

  • Function: Photosynthesis

  • Types:

    • Simple Leaf – Single undivided blade

    • Compound Leaf – Multiple leaflets

  • Specialized Leaves:

    1. Tendrils (climbing)

    2. Spines (protection)

    3. Storage Leaves (water retention)

    4. Reproductive Leaves (produce plantlets)



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Untitled Flashcards Set

Chapter 26: Phylogeny and the Tree of Life

Phylogenies Show Evolutionary Relationships

1. Define phylogeny and explain how phylogenies are used.

  • Phylogeny: The evolutionary history of a species or group of related species.

  • Use of phylogenies: Helps scientists understand evolutionary relationships and construct phylogenetic trees.

2. Define systematics.

  • Systematics: A branch of biology that classifies organisms and determines their evolutionary relationships.

3. What is binomial nomenclature?

  • A system for naming species using two parts: genus and species.

4. What are the two components of every binomial name?

  • Genus (capitalized)

  • Species (lowercase)

Taxonomy and Classification

5. What are the taxonomic categories in hierarchical order?

  • Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

  • Mnemonic: Dear King Philip Came Over For Good Spaghetti

6. Which organisms are more closely related: those in the same phylum or the same order?

  • Same order → More specific category than phylum.

Understanding Phylogenetic Trees

7. What does a branch point in a phylogenetic tree represent?

  • A common ancestor from which two lineages diverged.

8. Define sister taxa.

  • Sister taxa: Groups that share an immediate common ancestor and are each other's closest relatives.

9. How can a phylogenetic tree be drawn differently while still showing the same information?

  • It can be horizontal, vertical, or diagonal—only the branching pattern matters, not the orientation.

10. In a phylogenetic tree, are humans more closely related to frogs or lizards? Explain.

  • Lizards → Humans and lizards share a more recent common ancestor than humans and frogs.

11. What does it mean for a phylogenetic tree to be rooted?

  • A rooted tree has a branch representing the most recent common ancestor of all taxa in the tree.

12. Why are fishes considered the basal taxon?

  • They are the earliest diverging lineage in a given tree.

13. Three key points about phylogenetic trees that cannot be determined:
a. Actual ages of species
b. Exact amount of genetic change
c. Whether one taxon evolved from another

Inferring Phylogenies from Morphological and Molecular Data

14. How are phylogenetic trees inferred?

  • By analyzing morphological (physical) and molecular (DNA/protein) similarities.

15. Differentiate between homologous and analogous structures.

  • Homologous: Similar due to shared ancestry (e.g., whale fin & bat wing).

  • Analogous: Similar due to convergent evolution (e.g., bird wing & butterfly wing).

16. Why is it important to distinguish homologous from analogous structures?

  • Only homologous traits should be used to infer evolutionary relationships.

17. How can DNA homologies be determined after genetic changes?

  • By aligning gene sequences and identifying conserved regions.

18. If species A and B look alike but have different gene sequences, while species B and C look different but have similar gene sequences, which are more closely related?

  • B and C (genetic similarity is more reliable than appearance).

Constructing Phylogenetic Trees Using Shared Characters

19. What is a clade?

  • A group including an ancestor and all its descendants (monophyletic group).

20. Why is Group I monophyletic?

  • It includes a single ancestor and all its descendants.

21. Why is Group II paraphyletic?

  • It includes an ancestor but not all descendants.

22. Why is Group III polyphyletic?

  • It includes taxa with different ancestors.

23. What is a shared derived character?

  • A new trait that evolved in a clade but not in ancestors.

24. Why is hair a shared derived character for mammals but a backbone is not?

  • Hair evolved in mammals only (derived), while backbones appeared earlier (ancestral).

25. Why is a lancelet considered the outgroup in Figure 26.12?

  • It shares the fewest derived characters with the other taxa.

26. What animals belong to a clade starting with four limbs?

  • Amphibians, reptiles, birds, and mammals.

Using Maximum Parsimony in Evolutionary Biology

27. How does maximum parsimony apply to phylogenetic trees?

  • The simplest explanation (fewest evolutionary changes) is most likely correct.

28. What does a phylogenetic tree represent?

  • A hypothesis about evolutionary relationships.

29. What evidence suggests birds are closely related to crocodiles?

  • DNA, fossil evidence, and shared derived traits (e.g., similar heart structure, nest-building behavior).

Genomic Evidence of Evolutionary History

30. How does a genome help determine evolutionary relationships?

  • DNA sequences reveal genetic similarities and divergence over time.

31. Which method shows fungi are more closely related to animals than plants?

  • rRNA gene comparison (changes slowly over time).

32. Which method reveals Native American ancestry?

  • Mitochondrial DNA (mtDNA) (evolves quickly).

33. What are orthologous genes?

  • Genes in different species from a common ancestor (e.g., human and mouse hemoglobin genes).

34. What are paralogous genes?

  • Genes duplicated within a species that evolve independently (e.g., human hemoglobin genes).

35. Why are mice good model organisms for studying human diseases?

  • They share many homologous genes with humans.

36. What does it mean when genes are conserved?

  • They remain unchanged over time, indicating descent from a common ancestor.

Molecular Clocks and Evolutionary Time

37. What are molecular clocks?

  • Models that estimate the time of evolutionary divergence based on DNA mutations.

38. How do molecular clocks work?

  • Assume mutations accumulate at a constant rate over time.

39. When did HIV emerge according to molecular clocks?

  • Around 1930.

40. Two problems with molecular clocks:
a. Mutation rates are not always constant.

Chapter 29: Plant Diversity I: How Plants Colonized Land

29.1 Key Derived Characters of Plants

  • Plants evolved from green algae (charophytes).

  • Five Key Traits Shared with Green Algae:

    1. Rings of cellulose-synthesizing proteins

    2. Peroxisome enzymes

    3. Structure of flagellated sperm

    4. Formation of a phragmoplast

    5. Sporopollenin (prevents drying out)

  • Sporopollenin: A polymer that protects spores and zygotes from drying out, allowing colonization of land.

  • Alternation of Generations (Life Cycle):

    • Key Events: Fertilization and meiosis

    • Gametophyte (n) → produces gametes via mitosis

    • Sporophyte (2n) → produces spores via meiosis

  • Derived Traits of Plants for Terrestrial Life:

    1. Sporangia: Organs where spores are produced

    2. Spores: Haploid cells that grow into gametophytes

    3. Cuticle: Waxy layer that prevents water loss

    4. Apical meristems: Regions of active growth in roots and shoots

    5. Stomata: Pores for gas exchange

    6. Vascular tissue: Conducts water and nutrients

    7. Seed: A plant embryo with a food supply and protective coat

    8. Gymnosperms: Plants with "naked" seeds (e.g., pine trees)

    9. Angiosperms: Flowering plants with seeds in fruit (e.g., apple trees)

29.2 Life Cycle of Nonvascular Plants (Bryophytes)

  • Dominant Generation: Gametophyte (haploid, n)

  • Reproductive Structures:

    • Antheridium: Produces sperm

    • Archegonium: Produces eggs

  • Sporophyte (2n) produces spores via meiosis

  • Spore Dispersal: By wind or water

  • Fertilization: Requires water; sperm swims to egg

29.3 Seedless Vascular Plants

  • First plants to grow tall due to vascular tissue.

  • Types of Vascular Tissue:

    • Xylem: Transports water and minerals

    • Phloem: Transports sugars and nutrients

  • Competitive Advantage of Vascular Plants:

    • Grow taller → better access to sunlight

    • Structural support from lignin

  • Roots: Absorb water and anchor plants

  • Leaves: Increase surface area for photosynthesis

  • Dominant Generation: Sporophyte (diploid, 2n)

  • Moist Environment Required: Sperm needs water to reach the egg

Chapter 30: Plant Diversity II – The Evolution of Seed Plants

30.1 Seeds and Pollen Grains: Key Adaptations for Land

  • Three Components of a Seed

    1. Embryo – Young developing plant

    2. Food Supply – Provides nutrients

    3. Seed Coat – Protection

  • Five Common Characteristics of Seed Plants

    1. Reduced gametophyte stage

    2. Heterospory (microspores & megaspores)

    3. Ovules

    4. Pollen production

    5. Seeds

  • Why Pollen & Seeds Are Important for Land Adaptation

    • Pollen: Eliminates need for water for fertilization

    • Seeds: Provide protection & nourishment, allow dormancy

  • Advantages of Miniaturized Gametophytes

    1. Protection from environmental stress

    2. Dependent on sporophyte for nutrients

    3. No need for water for fertilization

    4. Enhanced dispersal mechanisms

  • Heterospory (Two Types of Spores & Their Development)

    • Megaspore → Develops into female gametophyte → Produces eggs

    • Microspore → Develops into male gametophyte → Produces sperm

  • Pollination Purpose

    • Transfer of pollen to ovules for fertilization

  • Advantages of Pollen Over Free-Swimming Sperm

    1. No dependence on water

    2. Increased dispersal distance

  • Advantages of Seeds Over Spores

    1. Can remain dormant until favorable conditions

    2. Contain stored food for the embryo

    3. Can be transported long distances

30.2 Gymnosperms: "Naked" Seeds on Cones

  • Four Phyla of Gymnosperms

    1. Cycadophyta (cycads)

    2. Ginkgophyta (Ginkgo biloba)

    3. Gnetophyta (Ephedra, Gnetum, Welwitschia)

    4. Coniferophyta (conifers: pines, firs, spruces)

  • Five Examples of Coniferophyta

    1. Pines

    2. Firs

    3. Spruces

    4. Redwoods

    5. Cedars

  • Gymnosperm Life Cycle (Pine Life Cycle Highlights)

    1. Sporophyte (tree) produces cones

    2. Male cones make pollen; female cones make ovules

    3. Wind pollination transfers pollen

    4. Fertilization occurs inside ovule

    5. Seed forms & disperses

    6. Seed germinates into new sporophyte

  • Why Gymnosperm Seeds Are "Naked"

    • They are not enclosed in fruits (develop on cone scales)

30.3 Angiosperms: Flowers & Fruits

  • What "Covers" Angiosperm Seeds?

    • Fruit (derived from ovary)

  • Function of Flowers

    • Specialized reproductive structures

    • Attract pollinators for fertilization

  • Parts of a Flower & Their Functions

    1. Sepals – Protect bud

    2. Petals – Attract pollinators

    3. Stamens (Anther + Filament) – Male reproductive structures

    4. Carpel (Stigma + Style + Ovary) – Female reproductive structures

  • Botanical Definition of a Fruit

    • Mature ovary that encloses seeds

  • Two Functions of Fruits

    1. Protect seeds

    2. Aid in dispersal

  • Cross-Pollination vs. Self-Pollination

    • Cross-Pollination: Pollen from one plant fertilizes another

    • Self-Pollination: Pollen fertilizes ovules of the same plant

  • Evolutionary Advantage of Cross-Pollination

    • Increases genetic variation

  • Double Fertilization (Two Events Occur)

    1. One sperm fertilizes egg → Forms zygote

    2. One sperm fertilizes central cell → Forms endosperm (food source)

  • Key Results of Double Fertilization

    1. Ovule → Seed

    2. Zygote → Embryo

    3. Endosperm → Nutrient tissue for embryo

  • Differences Between Monocots & Eudicots
    | Characteristic | Monocots | Eudicots |
    |---------------|---------|---------|
    | Cotyledons | 1 | 2 |
    | Leaf veins | Parallel | Net-like |
    | Flower parts | Multiples of 3 | Multiples of 4 or 5 |
    | Stem vascular bundles | Scattered | Arranged in a ring |

30.4 Human Welfare & Seed Plants

  • Importance of Seed Plants to Humans

    • Food: Grains, fruits, vegetables, nuts

    • Wood: Timber, paper, construction

    • Medicines: Many drugs derived from plants (e.g., aspirin from willow bark)

  • Threats to Plant Diversity

    1. Deforestation

    2. Habitat destruction

    3. Climate change

    4. Overharvesting

Test Your Understanding

  1. _________

  2. _________

  3. _________

  4. _________

  5. _________

  • Derived Characters on Phylogenetic Tree:

    • (a) Flowers

    • (b) Embryos

    • (c) Seeds

    • (d) Vascular tissue

Chapter 35: Plant Structure, Growth, and Development

35.1 Plant Structure and Organization

Hierarchy of Plant Body

  1. Organs: Root, Stem, Leaf

  2. Tissues: Dermal, Vascular, Ground

  3. Cells: Parenchyma, Collenchyma, Sclerenchyma, Xylem, Phloem

Roots

  • Functions: Anchorage, Water/Nutrient Absorption, Storage

  • Types:

    • Taproot System: One main root, deep soil penetration (e.g., dicots)

    • Fibrous Root System: Many small roots, prevents erosion (e.g., monocots)

  • Root Hairs: Increase surface area for absorption

Stems

  • Function: Support, Transport, Storage

  • Nodes: Points where leaves attach

  • Internodes: Stem segments between nodes

  • Buds:

    • Apical Buds: Primary growth (length)

    • Axillary Buds: Potential for new branches

Specialized Stems:

  1. Rhizomes – underground stems (e.g., ginger)

  2. Tubers – storage stems (e.g., potato)

  3. Stolons – horizontal stems (e.g., strawberries)

Leaves

  • Function: Photosynthesis

  • Types:

    • Simple Leaf – Single undivided blade

    • Compound Leaf – Multiple leaflets

  • Specialized Leaves:

    1. Tendrils (climbing)

    2. Spines (protection)

    3. Storage Leaves (water retention)

    4. Reproductive Leaves (produce plantlets)