Chapter 34: Vertebrates

Characteristic Traits of Chordates

Chordates are a diverse group of animals that share several key features distinguishing them from other animal phyla.

• Notochord: A flexible rod that provides structural support.

• Dorsal hollow nerve cord: Develops into the central nervous system.

• Pharyngeal slits: Openings in the pharynx that may develop into gills or other structures.

• Post-anal tail: An extension of the body past the anal opening.

Example: All vertebrates (including humans, birds, and fish) are chordates.

Function of Pharyngeal Slits

Pharyngeal slits serve different functions across chordate groups.

• In aquatic chordates, they often function in filter-feeding or respiration (as gills).

• In terrestrial vertebrates, they may develop into parts of the ear and throat.

Traits of Major Vertebrate Groups

Major vertebrate groups include fish, amphibians, reptiles, birds, and mammals. Each group has unique and shared traits.

• Fish: Aquatic, gills, scales.

• Amphibians: Moist skin, life cycle includes aquatic larval stage.

• Reptiles: Dry, scaly skin, lay amniotic eggs.

• Birds: Feathers, wings, lay amniotic eggs.

• Mammals: Hair, mammary glands, live birth (most).

Comparison: Birds and mammals are both endothermic (warm-blooded), but only birds have feathers.

Archaeopteryx and Bird Evolution

Archaeopteryx is a transitional fossil showing traits of both dinosaurs and modern birds.

• Feathers (like birds)

• Teeth and long bony tail (like reptiles)

Amniotic Egg Advantages

The amniotic egg is a key adaptation for terrestrial life.

• Protects embryo from desiccation

• Allows development away from water

Relative Age of Clades

Clades are groups of organisms with a common ancestor. Some clades have existed longer than others, influencing their diversity.

Convergent Evolution

Convergent evolution occurs when unrelated species evolve similar traits due to similar environmental pressures.

• Example: Wings in bats and birds.

Extinction and Biodiversity

Mass extinctions reduce biodiversity, but can also open ecological niches for new species to evolve.

Clade Diversity and Extinction

Some clades become more diverse after extinction events due to adaptive radiation.

Traits Unique to Mammals

• Hair or fur

• Mammary glands

• Three middle ear bones

Monotremes, Marsupials, and Eutherians

These are the three main groups of mammals.

• Monotremes: Lay eggs (e.g., platypus)

• Marsupials: Pouch development (e.g., kangaroo)

• Eutherians: Placental mammals (e.g., humans)

Primate Traits and Benefits

• Opposable thumbs

• Forward-facing eyes

• Large brains

Evolutionary Relationships: Homo sapiens and Homo neanderthalensis

Modern humans (Homo sapiens) and Neanderthals (Homo neanderthalensis) share a recent common ancestor and some genetic traits.

Evolution of Traits

Traits can become more common through natural selection if they confer survival or reproductive advantages.

Major Traits of Homo Species

• Bipedalism

• Large brain size

• Tool use

Chapter 35: Plant Structure, Growth, and Development

Plant Tissues and Functions

Plants have three main tissue types: dermal, vascular, and ground tissue.

• Dermal tissue: Protection

• Vascular tissue: Transport of water and nutrients (xylem and phloem)

• Ground tissue: Photosynthesis, storage, support

Xylem and Phloem

Xylem transports water and minerals from roots to shoots; phloem transports sugars throughout the plant.

Function of Root Hairs

Root hairs increase surface area for water and nutrient absorption.

Apical Dominance

Apical dominance is the inhibition of lateral bud growth by the apical bud, regulated by plant hormones.

Root Zones

• Zone of cell division

• Zone of elongation

• Zone of maturation

Secondary Growth

Secondary growth increases the thickness of stems and roots, mainly in woody plants.

Tree Rings and Climate

Tree rings are formed by variations in growth rate due to seasonal changes.

ABC Model of Flower Development

The ABC model explains how combinations of gene activities specify floral organ identity.

• A genes: Sepals

• A + B genes: Petals

• B + C genes: Stamens

• C genes: Carpels

Example: If a gene is nonfunctional, the corresponding organ may not develop.

Chapter 36: Transport in Plants

Transport Mechanisms

Plants use several mechanisms to move water and nutrients.

• Active transport: Requires energy

• Passive transport: Diffusion/osmosis

• Bulk flow: Movement due to pressure differences

Plant Multicellularity

Plants are multicellular organisms with specialized cells and tissues that function together.

Water Movement in Trees

Water moves from roots to leaves via xylem, driven by transpiration and cohesion-tension.

Transpiration and Water Potential

Transpiration is the loss of water vapor from leaves, creating negative pressure that pulls water upward.

Equation:

Where is water potential, is solute potential, and is pressure potential.

Protective Structures in Plants

• Casparian strip: Prevents uncontrolled flow of water and solutes into the vascular system.

• Cuticle: Waxy layer that reduces water loss.

Stomata Function

Stomata are pores that regulate gas exchange and water loss by opening and closing.

Chapter 38: Angiosperm Reproduction

Development and Function of Reproductive Structures

Angiosperms have flowers with male (stamens) and female (carpels) reproductive organs.

• Gametophyte: Haploid generation producing gametes

• Sporophyte: Diploid generation producing spores

Double Fertilization

Double fertilization is unique to angiosperms, involving two sperm cells:

• One fertilizes the egg (forms zygote)

• One fuses with two polar nuclei (forms endosperm)

Meiosis in Gamete Formation

Meiosis produces haploid gametes in both male and female organs.

Pollination Mechanisms

Pollination can occur via wind, water, or animals. Self-pollination and cross-pollination have different genetic outcomes.

Self-Fertilization and Disadvantages

Self-fertilization reduces genetic diversity, which can make populations more vulnerable to disease and environmental changes.

Chapter 39: Plant Responses to Internal and External Signals

Plant Hormones

Plant hormones regulate growth, development, and responses to stimuli.

• Auxins: Promote cell elongation

• Gibberellins: Stimulate stem elongation, seed germination

• Cytokinins: Promote cell division

• Abscisic acid: Induces dormancy, closes stomata

• Ethylene: Promotes fruit ripening

Photoperiodism

Photoperiodism is the response of plants to the length of day and night, affecting flowering and other processes.

Phototropism and Experiments

Phototropism is the growth of a plant toward light, regulated by auxin distribution.

• Experiment: If a plant tip is covered, it does not bend toward light; if the tip is removed, no response occurs.

Signal Transduction in Plants

Plants perceive signals and transduce them into cellular responses, often involving hormone signaling pathways.

Experimental Conclusions

Experiments demonstrate the roles of hormones and environmental factors in plant growth and development.

Additional info: Some explanations and examples were expanded for clarity and completeness based on standard General Biology curriculum.