Phylogeny, Prokaryotes, Protists, Plant and Animal Diversity: Structured Study Notes

Chapter 26: Phylogeny and the Tree of Life

Phylogeny and Classification

Phylogeny is the evolutionary history of a species or group of related species. Understanding phylogeny helps biologists classify organisms and trace their evolutionary relationships.

• Carolus Linnaeus: Developed the two-part binomial system for naming species (Genus species).

• Taxonomic Hierarchy: Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species.

• Phylogenetic Trees: Diagrams that represent evolutionary relationships; each branch point represents a common ancestor.

• Sister Taxa: Groups that share an immediate common ancestor.

Homology vs. Analogy

• Homology: Similarity due to shared ancestry (e.g., vertebrate forelimbs).

• Analogy: Similarity due to convergent evolution, not common ancestry (e.g., wings of birds and insects).

• Convergent Evolution: Independent evolution of similar traits in distantly related organisms.

Clades and Group Types

• Clade: A group of organisms that includes an ancestor and all its descendants.

• Monophyletic Group: Includes ancestor and all descendants.

• Paraphyletic Group: Includes ancestor and some, but not all, descendants.

• Polyphyletic Group: Includes taxa with different ancestors.

Character States and Tree Construction

• Ancestral Characteristics: Traits present in the ancestor.

• Derived Characteristics: Traits unique to a clade.

• Maximum Parsimony: Principle that the simplest explanation (fewest evolutionary events) is preferred.

• Phylogenetic Trees as Hypotheses: Trees are scientific hypotheses about relationships.

The Three Domains and Horizontal Gene Transfer

• Three Domains: Bacteria, Archaea, Eukarya.

• Horizontal Gene Transfer: Movement of genes between organisms other than by descent.

Chapter 27: Bacteria and Archaea

Prokaryotic Cell Structure

Prokaryotes are unicellular organisms lacking a nucleus. They have diverse cell wall structures and metabolic capabilities.

• Cell Wall: Maintains cell shape and protects against osmotic stress.

• Plasmolysis: Loss of water from a cell in a hypertonic environment.

• Peptidoglycan: Major component of bacterial cell walls; absent in archaea.

• Bacterial vs. Archaeal Cell Walls: Bacteria have peptidoglycan; archaea have unique polysaccharides and proteins.

• Gram Stain: Distinguishes gram-positive (thick peptidoglycan) from gram-negative (thin peptidoglycan, outer membrane) bacteria.

• Endospores: Resistant structures formed by some bacteria for survival.

• Fimbriae and Pili: Surface appendages for attachment and DNA transfer.

• Taxis: Directed movement toward or away from stimuli.

Internal Organization and Genetics

• Nucleoid: Region containing the prokaryotic chromosome.

• Binary Fission: Asexual reproduction by cell division.

• Transformation: Uptake of DNA from environment.

• Transduction: DNA transfer via bacteriophages.

• Conjugation: DNA transfer between cells via pili.

Metabolic Diversity

• Phototrophs: Use light as energy source.

• Chemotrophs: Use chemicals as energy source.

• Autotrophs: Use CO2 as carbon source.

• Heterotrophs: Use organic compounds as carbon source.

Table 27.1: Nutritional Modes of Prokaryotes

Energy Source	Carbon Source	Type	Example
Light	CO2	Photoautotroph	Cyanobacteria
Light	Organic compounds	Photoheterotroph	Rhodobacter
Chemicals	CO2	Chemoautotroph	Some Sulfur Bacteria
Chemicals	Organic compounds	Chemoheterotroph	Most bacteria
Additional info: Table entries inferred for completeness.

Oxygen Requirements and Ecology

• Aerobes: Require oxygen.

• Anaerobes: Do not require oxygen; may be obligate or facultative.

• Biofilms: Surface-coating colonies of prokaryotes.

• Cyanobacteria: Only bacterial group covered; important photoautotrophs.

• Extremophiles: Archaea adapted to extreme environments (halophiles, thermophiles).

• Decomposers: Break down dead organic matter.

• Symbiosis: Close association between organisms.

• Exotoxins: Secreted toxins.

• Endotoxins: Toxins released when bacteria die.

• Bioremediation: Use of organisms to remove pollutants.

Chapter 28: Protists

What are Protists?

Protists are a diverse group of mostly unicellular eukaryotes. They exhibit varied modes of nutrition and locomotion.

• Phototrophs: Obtain energy from light.

• Heterotrophs: Obtain energy from organic matter.

• Mixotrophs: Combine photosynthesis and heterotrophy.

• Endosymbiosis: Origin of some organelles (e.g., mitochondria, chloroplasts) from engulfed prokaryotes.

• Pseudopodia: Extensions of cytoplasm for movement.

• Cilia: Short, hair-like structures for movement.

Protist Taxonomy: Four Supergroups

• Excavata: Includes Diplomonads and Euglenazoans (e.g., Euglenids).

• SAR: Includes Stramenopiles (Diatoms, Brown Algae), Alveolata (Dinoflagellates, Apicomplexans, Ciliates), and Rhizaria (Radiolarians, Foraminiferans).

• Archaeplastida: Includes Red Algae, Green Algae (Charophytes), and Plants.

• Unikonta: Includes Amoebozoa (Entamoebas), Opisthokonts (Animals, Fungi, Choanoflagellates).

Table: Protist Supergroups and Examples

Supergroup	Representative Taxa	Key Features
Excavata	Diplomonads, Euglenazoans	Flagella, modified mitochondria
SAR	Diatoms, Brown Algae, Dinoflagellates, Ciliates, Forams	Diverse modes of nutrition, complex life cycles
Archaeplastida	Red Algae, Green Algae, Plants	Photosynthetic, plant ancestors
Unikonta	Amoebozoa, Opisthokonts	Amoeboid movement, includes animals and fungi

Chapter 29: Plant Diversity I

Origins and Traits of Plants

Plants evolved from green algae (charophytes) and share several derived traits that distinguish them from their ancestors.

• Derived Traits: Alternation of generations, apical meristems, cuticles, stomata, vascular tissue.

• Alternation of Generations: Life cycle alternates between multicellular haploid (gametophyte) and diploid (sporophyte) stages.

• Apical Meristems: Regions of cell division at tips of roots and shoots.

• Cuticle: Waxy covering that prevents water loss.

• Stomata: Pores for gas exchange.

Plant Groups

• Bryophytes: Non-vascular plants (liverworts, mosses, hornworts); dominant gametophyte, sporophyte attached.

• Seedless Vascular Plants: Lycophyta (club mosses, spike mosses, quillworts), Monilophyta (ferns, horsetails, whisk ferns); dominant sporophyte, independent gametophyte.

• Rhizoids: Root-like structures in bryophytes.

• Flagellated Sperm: Require water for fertilization.

• Peat Moss: Used for fuel, soil conditioner; stores carbon.

• Roots and Leaves: Vascular plants have true roots and leaves; leaves classified as microphylls or megaphylls.

• Megaspores vs. Microspores: Megaspores develop into female gametophytes; microspores into male gametophytes.

• Spores vs. Seeds: Spores are single cells; seeds are multicellular, contain embryo and food supply.

Chapter 30: Plant Diversity II

Seed Plants and Reproduction

Seed plants include gymnosperms and angiosperms, distinguished by their reproductive structures and adaptations.

• Seeds: Embryo, food supply, protective coat.

• Megasporophylls vs. Microsporophylls: Female vs. male spore-producing structures.

• Ovule: Structure containing female gametophyte.

• Pollen: Male gametophyte; pollen tubes deliver sperm.

• Advantages of Seeds: Dormancy, dispersal, protection, food supply.

Gymnosperms and Angiosperms

• Gymnosperms: "Naked seeds"; includes Cycadophyta, Ginkophyta, Gnetophyta (Welwitschia, Ephedra), Coniferophyta.

• Angiosperms: "Flowering plants"; seeds enclosed in fruit.

• Flowers: Reproductive organs; modified leaves.

• Female Parts: Carpel (stigma, style, ovary).

• Male Parts: Stamen (anther, filament).

• Double Fertilization: One sperm fertilizes egg, another forms endosperm.

• Cotyledons: Seed leaves; monocots (one), dicots (two).

• Endosperm: Food supply for embryo.

• Angiosperms and Animals: Pollination and seed dispersal.

• Monocots vs. Dicots: Monocots have parallel veins, fibrous roots; dicots have netted veins, taproot.

Table: Monocots vs. Dicots (Fig 30.16)

Feature	Monocots	Dicots
Cotyledons	1	2
Leaf Veins	Parallel	Netted
Root System	Fibrous	Taproot
Flower Parts	Multiples of 3	Multiples of 4 or 5
Additional info: Table entries inferred for completeness.

Chapter 32: Animal Diversity

What are Animals?

Animals are multicellular, heterotrophic eukaryotes with specialized tissues and complex development.

• Development: Cleavage → Blastula → Gastrula → Larva → Metamorphosis.

• Choanoflagellates: Closest living relatives to animals.

• Cambrian Explosion: Rapid diversification of animal forms.

• Symmetry: Asymmetrical, radial, bilateral.

• Tissues: Ectoderm (outer), endoderm (inner), mesoderm (middle).

• Diploblastic: Two tissue layers; Triploblastic: Three layers.

• Coelom: Body cavity lined by mesoderm.

• Hemocoel: Body cavity with blood-like fluid.

• Protostome vs. Deuterostome: Differences in embryonic development; protostomes form mouth first, deuterostomes form anus first.

• Archenteron: Primitive gut.

• Blastopore: Opening of archenteron.

Table: Animal Relationships

Group	Key Features
Eumetazoa	True tissues
Bilaterians	Bilateral symmetry, three tissue layers
Deuterostomia	Deuterostome development
Ecdysozoa	Molting (ecdysis)
Lophotrochozoa	Lophophore or trochophore larva

Chapter 33: Invertebrates

Invertebrate Diversity

Invertebrates are animals without a backbone, comprising the majority of animal species.

• Phylum Porifera: Sponges; sessile, filter feeders, lack true tissues, have choanocytes.

• Eumetazoa: All animals with true tissues.

• Phylum Cnidaria: Corals, jellies, hydra; radial symmetry, diploblastic, gastrovascular cavity, polyps and medusa, cnidocytes and nematocysts.

• Lophotrochozoa: Includes Platyhelminthes, Mollusca, Annelida.

• Phylum Platyhelminthes: Flatworms; bilateral symmetry, no body cavity, planarians (free-living), trematodes and tapeworms (parasitic).

• Phylum Mollusca: Snails, clams, squids, octopuses; foot, visceral mass, mantle, radula, chitons, gastropods, bivalves, cephalopods.

• Phylum Annelida: Segmented worms; coelom, errantians (marine), sedentarians (leeches, earthworms).

• Ecdysozoa: Includes Nematoda and Arthropoda; cuticle, molting (ecdysis).

• Phylum Nematoda: Roundworms; no circulatory system, only longitudinal muscles.

• Phylum Arthropoda: Exoskeleton, jointed appendages, trilobites, chelicerates (spiders, scorpions), myriapods (centipedes, millipedes), pancrustaceans (insects, crustaceans).

• Phylum Echinodermata: Sea stars, sea urchins, sand dollars; bilateral symmetry as larvae, water vascular system, tube feet.

Chapter 34: Vertebrates

Vertebrate Characteristics and Taxonomy

Vertebrates are animals with a backbone, belonging to Phylum Chordata. They exhibit complex structures and diverse adaptations.

• Phylum Chordata: Bilateral, deuterostomes; four key characteristics: notochord, dorsal hollow nerve cord, pharyngeal slits/clefts, post-anal tail.

• Cephalochordata: Lancelets.

• Urochordata: Tunicates (sea squirts).

• Vertebrata: All vertebrates.

• Jawless Vertebrates: Hagfish, lampreys.

• Gnathostomata: Jawed vertebrates; jaws evolved from modified pharyngeal slits.

• Chondrichthyes: Sharks, rays, ratfish; cartilaginous skeleton, large oily liver for buoyancy.

• Ray-finned Fishes (Actinopterygii): Most fish; bony endoskeleton, operculum, swim bladder.

• Lobe-finned Fishes (Sarcopterygii): Coelacanths, lung fishes, tetrapods.

• Tetrapods: Evolved from lobe-finned fishes; four limbs, Tiktaalik as transitional fossil.

• Amphibians: Salamanders (paedomorphosis), frogs (development), caecilians (no limbs); tied to water for reproduction.

• Amniotes: Amniotic egg allows reproduction away from water.

Additional info: Academic context and table entries were inferred for completeness and clarity. These notes cover all key concepts listed in the provided chapters, organized for exam preparation.