Plant Structure and Life Cycle

Plant Structures and Functions

• Chloroplasts contain chlorophyll and are responsible for photosynthesis
• Cell walls are made of cellulose and provide structural support
• Specialized reproductive organs include flowers and cones
• Vascular tissues (xylem and phloem) facilitate water and nutrient transport

Alternation of Generations in Plants

• Involves a cycle between a haploid gametophyte generation (producing gametes) and a diploid sporophyte generation (producing spores)
• Allows for both sexual and asexual reproduction

Transition from Water to Land in Plants

• Major adaptations include:
  • Development of a cuticle to prevent water loss
  • Roots for anchorage and absorption of water and nutrients
  • Vascular tissues for internal transport

Leaf and Plant Structures

• Cuticle: reduces water loss
• Stomata: regulate gas exchange
• Chloroplasts: contain chlorophyll for photosynthesis
• Cell walls: provide structural support
• Grana: sites of photosynthesis
• Stroma: involved in the synthesis of organic molecules

Evolution of Plant Structures

• Order of appearance: cuticle, stomata, roots, seeds, and finally flowers

Sporophyte and Gametophyte Generations

• In bryophytes, the gametophyte is dominant
• In ferns and gymnosperms, the sporophyte is dominant
• In angiosperms, the gametophyte generation is greatly reduced

Characteristics Unique to Animals

• Multicellularity
• Heterotrophy
• Locomotion
• Nervous system
• Sexual reproduction

Cladogram and Phyla

• A cladogram can be used to recognize which phyla possess a given characteristic

Transition from Water to Land in Animals

• Key adaptations include:
  • Development of limbs for movement
  • Lungs for respiration
  • Skin adaptations to prevent desiccation

Symmetry in Animals

• Bilateral symmetry offers better mobility, efficient hunting, and directional movement compared to spiral symmetry
• Bilateral symmetry is associated with triploblastic animals (three germ layers: ectoderm, endoderm, and mesoderm)
• Radial symmetry is associated with diploblastic animals (two germ layers: ectoderm and endoderm)

Protostomes and Deuterostomes

• Protostomes: blastopore develops into the mouth, and the anus forms later (e.g., mollusks, annelids, and arthropods)
• Deuterostomes: blastopore develops into the anus, and the mouth forms later (e.g., echinoderms and chordates, including vertebrates)

Asexual Reproduction

• Animals: budding (e.g., Hydra), fragmentation (e.g., starfish), and parthenogenesis (e.g., some lizards)
• Plants: vegetative propagation (e.g., runners in strawberries), fragmentation (e.g., spider plants), and budding (e.g., yeast)

Sexual Reproduction

• Advantages: genetic diversity, elimination of deleterious mutations through recombination
• Disadvantages: energy and time required to find a mate and produce offspring, risk of producing unfit offspring, and potential for genetic variability