BSC1011+Chapter+29+PowerPoint
Plant Diversity Ⅰ: How Plants Colonized Land
Chapter Overview
- This chapter from Campbell's Biology Twelfth Edition discusses the evolution of plants and their adaptation to terrestrial environments. It covers the ancestry of plants, their key characteristics, adaptations for land colonization, and the distinction between different plant groups.
Page 1: Introduction to Plant Diversity
- Title: Plant Diversity Ⅰ: How Plants Colonized Land.
- Copyright notice indicating that all rights are reserved by Pearson Education, Inc.
Page 2: Early Land Life
- Figure 29.1a:
- For most of Earth's history, the land surface was lifeless.
- Prokaryotes inhabited land approximately 3.2 billion years ago.
- Small plants, fungi, and animals appeared on land around 500 million years ago.
- By 385 million years ago, the first forests emerged (different species than present).
Page 3: Major Developments in Plant Evolution
- Figure 29.1b: Exploration of the major developments in plant evolution over time.
Page 4: Evolution from Green Algae
- Concept 29.1:
- Plants evolved from green algae (specifically, charophytes are the closest relatives).
- There are over 325,000 known plant species today, most of which are terrestrial.
- Plants provide essential roles: oxygen production, food sources, and habitat for terrestrial organisms.
Page 5: Evidence of Algal Ancestry (1 of 3)
- Plants and some algae share many traits:
- Both are multicellular, eukaryotic, and photosynthetic autotrophs.
- Both groups contain cellulose in their cell walls.
- Both groups have chloroplasts with chlorophyll a and b.
Page 6: Evidence of Algal Ancestry (2 of 3)
- Shared traits specifically with charophytes include:
- Arrangement of cellulose-synthesizing membrane proteins in rings.
- Similarities in the structure of flagellated sperm.
- Sequence similarities in nuclear, chloroplast, and mitochondrial DNA.
Page 7: Rings of Cellulose-Synthesizing Proteins
- Figure 29.2: Illustrates the rings of cellulose-synthesizing proteins in plants.
Page 8: Evidence of Algal Ancestry (3 of 3)
- Recent genetic studies show that the Zygnematophyceae clade of charophytes is the closest living relative of land plants.
- Although modern charophytes are not ancestors of land plants, they share common ancestry.
Page 9: Zygnema Alga
- Figure 29.3: Depicts Zygnema, an alga closely related to land plants.
Page 10: Adaptations for Terrestrial Life (1 of 3)
- Charophytes possess a coating of sporopollenin, a polymer that prevents zygote desiccation.
- Sporopollenin is also a component of the protective walls of plant spores.
Page 11: Adaptations for Terrestrial Life (2 of 3)
- Transitioning to land offered advantages:
- Access to unfiltered sunlight.
- Increased availability of carbon dioxide (CO₂).
- Nutrient-rich soils.
- However, land also presented challenges:
- Scarcity of water.
- Insufficient structural support against gravity.
- The evolution of adaptations allowed plants to diversify and thrive despite these challenges.
Page 12: Adaptations for Terrestrial Life (3 of 3)
- The classification of plants remains debated, particularly the boundary between plants and algae.
- Traditional definitions equate the kingdom Plantae with embryophytes (plants with embryos).
Page 13: Possible Plant Kingdoms
- Figure 29.4: Proposes three potential kingdoms of plants: Viridiplantae, Streptophyta, and Plantae.
Page 14: Derived Traits of Plants (1 of 6)
- Four key traits appear almost universally in plants but are absent in charophytes:
- Alternation of generations: A unique lifecycle featuring alternating multicellular forms.
- Walled spores produced in sporangia: Specialized structures for spore production.
- Apical meristems: Regions of active cell division at the tips of roots and shoots.
Page 15: Alternation of Generations Defined
- Alternation of Generations: This term refers to a plant life cycle characterized by the alternation between two multicellular forms:
- The haploid gametophyte, which produces gametes (sperm and eggs) via mitosis.
- The diploid sporophyte, which produces haploid spores through meiosis.
- Spores develop into gametophytes, whereas fertilized eggs (zygotes) develop into sporophytes.
Page 16: Exploring Alternation of Generations (1 of 4)
- Diagram illustrating the alternation of generations process, highlighting the life cycle transitions between gametophytes and sporophytes.
Page 17: Exploring Alternation of Generations (2 of 4)
- Continuation of the diagram illustrating the alternation of generations in plants.
Page 18: Exploring Alternation of Generations (3 of 4)
- Multicellular, Dependent Embryos: The diploid embryo remains protected within the female gametophyte's tissue.
- Nutrient transfer from the parent to the embryo is facilitated by placental transfer cells.
- This dependency on the parent leads to the term embryophytes.
Page 19: Exploring Alternation of Generations (4 of 4)
- Continuation of the previous diagrams exploring alternation of generations in plants.
Page 20: Walled Spores Produced in Sporangia
- The sporophyte forms spores within multicellular structures called sporangia.
- The spore walls contain sporopollenin, which enhances their durability under harsh environmental conditions.
Page 21: Moss Sporophytes and Sporangia
- Figure 29.6: Example showing sporophytes and sporangia of a moss from the genus Mnium.
Page 22: Apical Meristems
- Apical Meristems: Defined as localized regions at the tips of roots and shoots where cell division occurs.
- These continuously dividing cells enable the elongation of roots and shoots, thus improving resource acquisition for the plant.
Page 23: Apical Meristem in Plant Shoots
- Figure 29.7: Illustrates the apical meristem of a plant shoot, displaying developing leaves.
Page 24: Additional Derived Traits of Plants (1 of 2)
- Derived traits of plants that support survival on land include:
- Cuticle: A waxy protective layer on the epidermis to reduce water loss.
- Stomata: Pores that enable gas exchange between the plant's internal tissues and the external environment.
Page 25: Additional Derived Traits of Plants (2 of 2)
- Early land plants lacked true roots and leaves, posing challenges for nutrient absorption from the soil.
- Fossils from approximately 420 million years ago suggest that symbiotic relationships with fungi (mycorrhizae) may have facilitated colonization of terrestrial environments by plants lacking roots.
Page 26: Origin and Diversification of Plants (1 of 9)
- Microorganisms first colonized land around 3.2 billion years ago.
- The first plant spores appeared in the fossil record around 470 million years ago.
- Fossilized spores within sporophyte tissues have been dated back to approximately 450 million years ago.
Page 27: Ancient Plant Spores and Tissues
- Figure 29.8: Showcases fossilized spores and sporophyte tissues, providing insight into early plant life.
Page 28: Evidence of Early Structures
- Fossils of larger plant structures, such as the Cooksonia sporangium, have been identified and dated to around 425 million years ago.
Page 29: Cooksonia Sporangium Fossil
- Figure 29.9: Displays the fossilized remains of a Cooksonia sporangium, revealing details about ancient plant reproduction.
Page 30: Ancestral Evolution
- Evolution of ancestral plant species contributed to the extensive diversity observed in contemporary plants on Earth.
Page 31: Classification of Extant Plants
- Table 29.1: Overview of ten phyla of extant plants and their respective species counts:
- Nonvascular Plants (Bryophytes):
- Phylum Hepatophyta (Liverworts): 9,000 species
- Phylum Bryophyta (Mosses): 13,000 species
- Phylum Anthocerophyta (Hornworts): 225 species
- Vascular Plants:
- Seedless Vascular Plants:
- Phylum Lycophyta (Lycophytes): 1,200 species
- Phylum Monilophyta (Monilophytes): 12,000 species
- Seed Plants:
- Phylum Ginkgophyta (Ginkgo): 1 species
- Phylum Cycadophyta (Cycads): 350 species
- Phylum Gnetophyta (Gnetophytes): 75 species
- Phylum Coniferophyta (Conifers): 600 species
- Phylum Anthophyta (Angiosperms): 290,000 species
Page 32: Highlights of Plant Evolution
- Figure 29.10: Timeline illustrating the origins of various plant groups:
- Origin of plants from ancestral green algae (470 mya).
- Origin of vascular plants (425 mya).
- Emergence of seed plants (360 mya).
- The rise of angiosperms (flowering plants).
Page 33: Vascular Plants
- Vascular plants possess specialized tissues for the transport of water and nutrients, enabling them to grow taller and colonize a variety of habitats.
Page 34: Nonvascular Plants
- Nonvascular plants, such as liverworts, mosses, and hornworts, lack extensive transport systems and are informally grouped as bryophytes.
- This grouping does not represent a monophyletic clade.
Page 35: Seedless Vascular Plants
- Seedless vascular plants have effective vascular systems but do not produce seeds. They are classified into:
- Lycophytes: Club mosses and relatives.
- Monilophytes: Ferns and relatives.
Page 36: Shared Biological Features
- Organisms can be grouped based on shared biological traits, though these may not reflect shared ancestry.
Page 37: Seed Plants Dominance
- Seed plants, characterized by being vascular plants that produce seeds, make up the majority of living plant species.
- A seed is defined as an embryo encapsulated in a nutrient-rich coating for protection.
Page 38: Types of Seed Plants
- Seed plants are divided primarily into two groups:
- Gymnosperms: Produce seeds that are not enclosed in ovaries (termed “naked seeds”).
- Angiosperms: Produce seeds that develop within protective chambers called ovaries, which are part of flowers. Nearly 90% of living plant species are angiosperms.
Page 39: Life Cycles of Bryophytes
- Concept 29.2: The life cycle of mosses and other nonvascular plants is dominated by gametophytes.
- Bryophytes include three phyla: liverworts (Hepatophyta), mosses (Bryophyta), and hornworts (Anthocerophyta).
- This group diverged from other plant lineages early in plant evolution.
Page 40: Nonvascular Plant Hierarchy
- Figure 29.UN01: Illustrative hierarchy categorizing nonvascular plants (bryophytes), seedless vascular plants, gymnosperms, and angiosperms.
Page 41: Dominance of Haploid Gametophytes
- In bryophytes, haploid gametophytes are the dominant life stage, typically larger and longer-lived than sporophytes.
- Sporophytes are often ephemeral and only present during part of the life cycle.
Page 42: Moss Life Cycle Diagram
- Figure 29.11: Diagram of the life cycle of a moss, detailing the phases of haploid gametophyte and diploid sporophyte, associated structures, and processes such as fertilization and meiosis.
Page 43: Moss Life Cycle Animation
- Visual aids such as animations explaining the moss life cycle enhance comprehension of life stage transitions.
Page 44: Spore Development in Bryophytes
- Upon dispersal to suitable habitats, bryophyte spores germinate, developing into a mass of green filaments called protonema.
- Protonema consist of one-cell-thick filaments that absorb water and nutrients and form buds that develop into gametophytes.
Page 45: Stature Constraints of Bryophytes
- Bryophytes typically have height restrictions due to:
- Absence of rigid support tissue.
- Lack of vascular systems for long-distance transport.
- Some moss species possess limited conducting tissues, enabling them to grow up to 60 cm (approximately 2 feet) tall.
Page 46: Anchorage Structures in Bryophytes
- Rhizoids are root-like structures in bryophytes that anchor them to substrates but lack specialized cells for water and nutrient absorption.
Page 47: Gametangia Production
- Gametophytes in bryophytes can produce multiple gam