Lecture 3-1: Plant and Animal Physiology and Development

Transport in Plants

Key Concepts

• Water Potential: Potential energy of water; water moves from high to low water potential.
• Two Transportation Systems:
  • Water transport
  • Solute transport

Water Transport System

• Stages of Water Movement:
  1. Soil to Root Cells: Low water potential in root cells draws water in from soil.
  2. Roots to Stems: Involves cohesion (water sticking to itself) and adhesion (water sticking to other substances), resulting in capillary action in xylem.
  3. Stems to Leaves: Transpiration causes water to evaporate from leaves, creating negative water potential, drawing water up from xylem.

Solute Transport System

• Key Terms:

  • Photosynthates: Sugars like sucrose produced by photosynthesis.
  • Sources: Cells producing photosynthates.
  • Sinks: Areas needing photosynthates (e.g., roots, young shoots, seeds).

• Transport Mechanism:

  1. Active Transport: Sugars moved from source to phloem, requiring energy.
  2. Osmosis: Water moves from xylem to phloem due to solute concentration, increasing phloem water potential.
  3. Movement to Sinks: Phloem contents move to sinks due to lower water potential.

Introduction to Animal Diversity

Features of the Animal Kingdom

• Heterotrophs: Organisms that consume organic substances.
• Complex Tissue Structures: Lack cell walls, have extracellular matrix.
• Diplotic Life Cycle: Only multicellular form is diploid.
• Motility: Most animals can move; some are sessile.
• Complex Development and Fixed Body Plan: Specific genetic programs guide development.
• Reproduction: Primarily sexual; some asexual reproduction exists.

Animal Embryonic Development

• Stages:
  1. Zygote: Divides without growing, forming cleavage.
  2. Blastula: 16-32 cell stage, can be hollow or filled with yolk.
  3. Gastrulation: Formation of blastopore leading to digestive tract and cell layers.

Hox Genes

• Role: Master control genes that direct body plan development.
• Conservation: Highly conserved across animal species; mutations lead to dramatic developmental changes.

Classification and Phylogeny of Animals

Symmetry

• Bilateral Symmetry: One plane of symmetry (e.g., humans).
• Radial Symmetry: Multiple planes of symmetry (e.g., coral polyp).
• No Symmetry: Seen in sponges.

Body Structure

• Diploblastic: Two cell layers (ectoderm, endoderm).
• Triploblastic: Three cell layers (ectoderm, mesoderm, endoderm).

Body Cavities in Triploblasts

• Acoelomates: No body cavity.
• Coelomates: Body cavity within the mesoderm.
• Pseudocoelomates: Body cavity between mesoderm and endoderm.

Protostomes vs. Deuterostomes

• Protostomes: Mouth forms first from blastopore.
• Deuterostomes: Anus forms first from blastopore.

Evolutionary Origins

• Origin of Animals: Likely evolved from colonial protists (choanoflagellates).
• Genetic Evidence: Sequencing aligns sponges more closely with choanoflagellates.

Next Lecture Preview

• Discussion on the evolutionary timeline of animal development.