Algae and Archaeplastida Clade

• Algae and Archaeplastida Clade

Protists

• Not plants, but photosynthetic
• Brown algae are multicellular, mostly marine, and haplodiplontic

Archaeplastida

• A true plant lineage including Red Algae (Rhodophyta), Green Algae (Chlorophyta & Charophyta), and Land Plants
• All obtained chloroplasts via primary endosymbiosis

Rhodophyta (Red Algae)

• Marine, multicellular, red due to phycoerythrin (absorbs blue light for deep water photosynthesis)
• Haplodiplontic, complex sexual + asexual cycles

Chlorophyta (Green Algae Group 1)

• Mostly freshwater, unicellular, paraphyletic group
• Life cycle mostly haplodiplontic, with some haplontic unicellular forms
• Example: Chlamydomonas (haplontic, 2 flagella, unicellular)
• Example: Ulva (sea lettuce), edible, haplodiplontic

Charophyta (Green Algae Group 2)

• Closest relatives to land plants

• Freshwater, haplontic, some multicellular

• Life cycle: zygote is only diploid cell (haplontic)

• Includes Charales (multicellular) and Coleochaetales (unicellular/colonial)

• Transition to Land Plants

Kingdom Viridiplantae

• Includes green algae + land plants (seedless plants: liverworts, mosses, hornworts, lycophytes, ferns/allies, and seed plants: gymnosperms and angiosperms)
• Land plants evolved from Charophytes
• Excludes Red Algae (a plant but not "green") and Brown Algae (cellular protists)

Key Adaptations for Land Life

• Desiccation Resistance: waxy cuticle + stomata

• Water/Nutrient Transport: xylem moves water from roots up; phloem transports sugars from leaves

• UV Protection: Diploid dominance helps mask mutations

• All land plants are haplodiplontic

• Gametophytes will experience a reduction of size

• Non-Vascular Plants (Bryophytes)

• Paraphyletic, closest descendants of the first land plants

• Lack vascular tissues (nontracheophytes)

• No true leaves- instead they have Phyllids which are leaf-LIKE structures found on the gametophyte stage

• Require water for sexual reproduction

• Life cycle: haplodiplontic

• Rhizoids: Root-like anchoring structures that do not actively extract minerals and water from the substrate, providing transport through diffusion and support

Liverworts (Hepaticophyta)

• Gametophyte is dominant
• Reproduces sexually (via gametangia) and asexually (gemmae cups)
• Haplodiplontic life cycle
• Archegonium (female), Antheridium (male), flagellated sperm must swim in water

Mosses (Bryophyta)

• Gametophyte = small leaf-like structure; sporophyte = brown vertical "stems"
• Gametangia form at the "leaf" tips of gametophytes
• Anchored to substrate by rhizoids (not true roots)
• Haplodiplontic life cycle

Hornworts

• Part of Bryophyte group

• Vascular Plants (Tracheophytes)

• Have xylem and phloem (vascular tissue)

• Monophyletic

• Evolved twice with 2 different solutions to maximize sugar production and its transport

• Gametophyte reduced in size relative to the sporophyte

• Sporophyte is dominant

• Still haplodiplontic

• Leaves increase surface area for photosynthesis in close contact with vessels

• Lycophylls: simple, one-veined leaves (Lycophytes)

• Euphylls aka "True Leaves": complex, branching veins (Ferns + Seed Plants)

Lycophytes (club mosses)

• Seedless, microphylls
• Monophyletic

Monilophytes (ferns + relatives)

• Ferns, Horsetails, Whisk Ferns

• Sporophyte large; gametophyte small; water needed for sperm travel

  • Meiosis takes place inside sporangia of sporophyte leaf
  • Gametophyte of ferns are tiny, usually without vessels or rhizoids
  • Archegonia/Antheridia - water needed for fertilization

• Monophyletic

• Whisk ferns: No leaves, tiny phyllids, no roots, rhizoids, photosynthetic stems, dichotomic growth

• Horsetail ferns: Photosynthetic stems, leaves arranged in whorls forming circles, leaves with a single vascular bundle

• Ferns have a haplodiplontic life-cycle

• Seed Plants

Gymnosperms ("Naked Seeds")

• No flowers or fruits of angiosperms
• Seeds are exposed on cones
• All have ovule exposed on a scale
• Include Pines, firs, spruces, cycads, ginkgos
  • Coastal redwood - tallest living vascular plant
  • Bristlecone pine - oldest living tree
• Fertilization takes ~15 months after pollination
• No double fertilization (synapomorphy of flowering plants)
• Female gametophyte: inside ovule, includes 2 archegonia (gametes)
  • Megagametophyte has many cells
• The Generative Cell of pollen divides through mitosis and produces 2 sperm cells (after it reaches the micropyle)
• The Tube Cell produces the pollen tube
• Male gametophyte (pollen)
  • Tube cell (makes pollen tube)
  • Generative cell → 2 sperm cells (via mitosis)
• One sperm fertilizes; the other degenerates (ONE YEAR AFTER POLLINATION)

Angiosperms ("Flowering Plants")

• Most diverse plant group

Key Features (Synapomorphies)

• Flowers
• Fruits
• Double Fertilization
• Carpel: A modified leaf (protective structure around ovule) that develops into fruit
• Ovules with 2 integuments
• Specialized phloem cells (with companion cells)
• Tricolpate pollen (in eudicots)

Flower Anatomy

• Flowers are organized in concentric circles called whorls
• Whorls:
  • Sepals (Outermost)
  • Petals (Second)
  • Stamens (Third)
  • Carpels (Innermost-"Gynoecium")
  • Stamens:
    • Filament (stalk) + Anther (pollen produced here)
    • Male
  • Carpels:
    • Houses the female gametophyte inside the ovule
    • The ovule is not a carpel; the ovule is not a gametophyte
    • 1 or more
    • Stigma (tip that receives pollen)
    • Style (tube/neck/stalk)
    • Ovary (contains ovules) swollen base containing ovules- later develops into a fruit
    • Ovule produces seeds and Ovary produces fruit
    • Female

Featured examples

• Tomates:
  • Have 2-3 fused carpels
  • Through plant breeding researchers have produced tomatoes with more than 3 carpels
• Legumes:
  • Have one single carpel

Female Gametophyte: Embryo Sac

• Located within the ovule inside the ovary of a flower
• Starts as Megaspore mother cell (2n) → then goes through meiosis → creating 4 haploid megaspores (only 1 survives)
• Surviving megaspore → 3 rounds of mitotic divisions → producing 8 nuclei arranged into 7 cells
  • 1 Egg cell will be fertilized to form the zygote
  • 2 synergids help guide the pollen tube to the egg
  • 3 antipodal cells; function not fully understood, may support embryo sac
  • 1 central cell (2 nuclei) contains 2 polar nuclei and will fuse with a sperm nucleus to form the triploid endosperm (3n)
• The structured form is called the embryo sac, which is the female gametophyte of angiosperms
• Entire development occurs within the sporophyte tissue of the flower

Male Gametophyte

• Pollen mother cell (2n) → meiosis → 4 microspores
• Microspores → mitosis → pollen (with tube cell + 2 sperm)

Double Fertilization

• 1 sperm fertilizes egg → zygote (2n)

• 1 sperm fuses with polar nuclei → endosperm (3n) (nourishes embryo)

• Animal Body Plans

Key Evolutionary Features of Animals

• Metazoans- Multicellular animals are traditionally divided into 35-40 distinct phyla based on shared anatomy and embryology (include sponges). Divided into two main branches (Parazoa and Eumetazoa)

Symmetry

• radial (Cnidaria) vs. bilateral (most animals)
  • Parazoa (sponges) lack any definite symmetry and lack tissues; also lack germ layers (Blastula, No Gastrula)
  • Eumetazoa (the rest of animals) have a symmetry defined along an imaginary axis drawn through the animal's body and true tissues
    • Diploblastic animals -develop 2 germ layers (ectoderm and endoderm) in the gastrula stage and lack a mesoderm, so they have no true muscles or complex organs (Cnidaria).
    • Triploblastic animals- Develop 3 germ layers (ectoderm, mesoderm, and endoderm) in the gastrula stage. Allows for more complex body structures (found in bilateral animals (from flatworms to humans).
  • Radial symmetry: body parts arranged around central axis; can be bisected into 2 equal halves in any 2-D plane
  • Bilateral symmetry: body has right and left halves that are mirror images; only the sagittal plane bisects the animal into 2 equal halves
• Greater mobility- can move in a consistent direction, typically anterior part leading
• Directional movement led to the grouping of nerve cells into a brain and sensory structures in the anterior part (cephalization or evolution of a definite brain area)

Tissues

• Parazoa (no tissues) vs. Eumetazoa (true tissues)
  • Parazoa (sponges- the simplest animals) lack defined tissues and organs, closely related to Choanoflagellates
  • Eumetazoa have distinct well-defined tissues

Body Cavities

• acoelomate, pseudocoelomate, coelomate
  • Body cavities allow more advanced organ systems to develop
  • During Embryonic development, the vast majority of Eumetazoa produce 3 germ layers
    • Outer Ectoderm (lead to body coverings and nervous system)
    • Middle Mesoderm (lead to skeleton and muscles)
    • Inner Endoderm (most organs and digestive tube)
  • Different from a digestive cavity, a body cavity is a space inside the embryo that is formed during development in many but not all Eumetazoa. Based on the type of body cavity, animals are divided into 3 groups
    • Acoelomates- No body cavity and organs are in direct contact with mesodermal tissue (ex. flatworms)
    • Pseudocoelomates- Body cavity between mesoderm and endoderm and does not develop within mesoderm but between mesoderm and endoderm; cavity is called the pseudocoelom
    • Coelomates- Body cavity is entirely within the mesoderm; originates from mesoderm cells and cavity is called the coelom

Development

• protostome (mouth first) vs. deuterostome (anus first)
  • Protostomes- develop the mouth first from or near the blastopore
    • Anus (if present) develops later either from blastopore or another region of embryo
    • Most bilaterians: flatworm (no anus), nematodes (no anus), mollusks, and arthropods
    • Spiral cleavage- each new cell cleaves off at an angle oblique to the polar axis; new cells are not aligned directly over each other
    • Adult cell fate is determined early; each early embryonic cell is destined to occur in a particular part of the adult body; if a cell of the blastula is eliminated, development cannot proceed
    • Coelom forms as soon as the gut (mouth) starts to develop
  • Deuterostomes- develop the anus first from the blastopore
    • Mouth develops later from another region of the embryo
    • Echinoderms, chordates (include vertebrates)
    • Radial cleavage- each new cell cleaves off along an axis that is parallel to the polar axis; new cells are aligned directly over each other
    • Indeterminate development- Adult cell fate is determined much later after the blastula is formed; if a cell of the blastula is eliminated, development proceeds and this cell is replaced with another through mitosis
    • Coelom forms much later (after most of the gut is formed)

Main Clades of Bilateria

• Protostomes, Deuterostomes, and Chaetogmata (forms its own monophyletic phylum)
  • All animals in Bilateria are Triploblastic and have bilateral symmetry
  • Most animals in Bilateria have a complete digestive tract
    • Protostomes- The first opening in embryonic development (blastopore) becomes the mouth
      • Split into:
        • Ecdysozoa: animals that molt (perform ecdysis) aka shed their exoskeleton: includes Nematodes, Arthropods, Crustaceans
        • Spiralia: animals that grow by gradual addition of body mass :
          • Lophotrochozoa: animals with lophophore feeding structures that move by muscular contraction: includes Annelida, Mollusca, Brachiopoda, Nemertea
          • Platyzoa: tiny, often flat-bodied animals that use cilia for movement: includes Flatworms (Platyhelminthes), Rotifers
    • Deuterostomes- The first opening becomes the anus, and the mouth forms second
      • Includes: Chordata (e.g., vertebrates) and Echinodermata (e.g., sea stars)
    • Annelids and Arthropods were once grouped together (both segmented), but DNA shows they belong in different clades:
      • Annelids → Lophotrochozoa (Spiralia → Protostomes)
      • Arthropods → Ecdysozoa (Protostomes)

The basic bilaterian

• All animals except sponges and Cnidaria pattern of development
• Mitotic cell divisions (cleavages) of the egg form a ball of cells, called the blastula (hollow sphere of cells)
• Blastula folds inward to form a 3-layer-thick ball (gastrula) with:
  • Blastopore- opening to outside
  • Archenteron- primitive body cavity
  • Ectoderm
  • Endoderm
  • Mesoderm
• Segmentation: evolved multiple times

The 3 Layers of a Sponge (Porifera)

• NO GERM LAYERS
  • Outer Epithelium:
    • Made of epithelial cells
    • Contains ostia (small pores) where water enters the sponge
    • Water flows in through ostia and out through the osculum (large opening at the top)
  • Mesohyl:
    • The gel-like middle layer between the outer layer and inner canal with "protein matrix"
    • Contains:
      • Spicules: structural support (made of calcium carbonate or silica)
      • Spongin: tough reinforcing protein fibers (makes sponges feel "spongy")
      • Amoebocytes: mobile cells that perform many functions: digest food, transport nutrients, help with reproduction
  • Inner Layer (Choanocyte Layer):
    • Lined with choanocytes (collar cells) - similar to Choanoflagellate
    • These cells have flagella that create water currents (water circulation) and trap food particles from the passing water

Sponge Reproduction

• Asexual Reproduction:
  • Fragmentation: A piece of sponge breaks off and grows into a new individual (a clone) and is common in stable environments where genetic variation isn't as critical
• Sexual Reproduction:
  • Amoebocytes (versatile cells in the mesohyl) can transform into sperm cells
  • These sperm cells are released into the water, and another sponge pulls them in through its pores during filter feeding
  • Inside the second sponge, choanocytes capture the sperm and deliver it to an egg cell in the mesohyl
  • Fertilization occurs in the mesohyl
• Larva Stage:
  • The fertilized egg develops into a free-swimming larva (usually ciliated for movement)
  • The larva swims away, settles on a surface, and grows into an adult sponge

Phylum Cnidaria

• Cnidarians are diploblastic animals (2 germ layers: ectoderm and endoderm)
• They have radial symmetry
• Examples: jellyfish, sea anemones, corals, hydra
• Cnidarian Body Structure Key body parts:
  • Epidermis: outer layer (from ectoderm)
  • Gastrodermis: inner layer lining the digestive cavity (from endoderm)
  • Mesoglea: jelly-like, non-cellular layer between the two — not a true tissue
  • Mouth: also serves as the exit (only one opening)
  • Gastrovascular cavity: digestive chamber; also handles gas exchange and waste; in some, it helps form gametes (sperm/egg)

Basic Body Forms

• Polyp (e.g., sea anemones, coral)
  • Cylindrical
  • Sessile (attached to a surface)
  • Mouth/tentacles face up
• Medusa (e.g., jellyfish)
  • Umbrella-shaped
  • Free-swimming
  • Mouth/tentacles face down

Skeleton in Polyps

• Many polyp species build exoskeletons around themselves for support
  • Can be made of: Chitin (a tough polysaccharide also found in fungi and arthropods) or Calcium carbonate (especially in corals)
• These structures also help form colonies, where multiple polyps are physically connected

Class Anthozoa (Phylum Cnidaria)

• Includes: Sea anemones, most corals, sea fans
• Exist only as polyps (no medusa form)
• Can be solitary (like a sea anemone) or colonial (like reef-building corals)

Coral Symbiosis with Zooxanthellae

• Corals have a mutualistic relationship with tiny protists called zooxanthellae
  • They are a type of dinoflagellate (single-celled algae)
  • They live inside coral tissue
  • The zooxanthellae photosynthesize, producing sugars
• In return, the coral provides protection and waste products (like nitrogen) that the algae use
• This gives coral its color - and when corals lose these algae (due to stress like warming oceans), they turn white ("coral bleaching")

Coral Reefs Importance

• Economically and ecologically:
  • Nursery/refuge for young fish
  • Protect shorelines by absorbing wave energy (barrier against storms/hurricanes)
  • Support huge marine biodiversity
• Protostomes
  • Split into two major groups:
    • Spiralia: Platyzoa (flatworms) + Lophotrochozoa (mollusks, annelids)
    • Ecdysozoa: Nematodes + Arthropods (molt exoskeleton)

Key Phyla Covered

• Platyhelminthes: flatworms, tapeworms, flukes

• Mollusca: gastropods, bivalves, cephalopods (closed circulatory in cephalopods)

• Annelida: segmented worms (earthworms, leeches)

• Nematoda: roundworms (many parasites like Trichinella)

• Arthropoda: insects, crustaceans, spiders — segmented, jointed limbs, chitin exoskeleton

• Deuterostomes & Vertebrate Evolution

Vertebrate Evolution Overview

• Chordate Ancestor gave rise to various vertebrate groups, including:
  • Jawless fish (e.g., hagfish, lampreys)
  • Cartilaginous fish (e.g., sharks)
  • Bony fish (ray-finned and lobe-finned)
  • Amphibians → Reptiles → Birds → Mammals

Class Amphibia

• First Vertebrates to Walk on Land: Descended from lobe-finned fish

Key Traits

• Legs: Adaptation for terrestrial locomotion
• Lungs: For breathing air
• Cutaneous Respiration: Gas exchange through moist skin
• Pulmonary Veins: Circulate oxygenated blood from lungs to heart
• Partially Divided Heart: Three chambers; improves separation of oxygenated and deoxygenated blood

Transitional Fossil: Tiktaalik

• Exhibits both fish and amphibian characteristics:
  • Gills and scales (like fish)
  • Neck and limb-like lobed fins with shoulder, forearm, and wrist bones (like amphibians)

Class Reptilia

• Over 7,000 species; evolved from amphibians

Key Traits

• Amniotic Egg: Contains membranes and a food source; watertight
• Dry, Keratinized Skin: Prevents water loss
• Thoracic Breathing: Expands ribcage to draw in air

Skull Types

• Anapsid: No temporal openings (e.g., turtles)
• Synapsid: One temporal opening (e.g., ancestors of mammals)
• Diapsid: Two temporal openings (e.g., most reptiles and birds)
  • Therapsids → Early Mammal-like Reptiles
    • Some were endothermic
    • Possibly had fur (keratin-based)
    • Gave rise to mammals

Class Aves (Birds)

• Evolved from theropod dinosaurs
• Approximately 8,600 species; most diverse group of terrestrial vertebrates

Shared Traits with Reptiles

• Amniotic Eggs: Protective and self-contained
• Scales on Legs: Similar to reptilian ancestors

Unique Traits

• Feathers: Made of keratin; provide insulation and enable flight
• Flight Skeleton:
  • Hollow bones reduce weight
  • Many bones are fused to provide strength
  • Large keel-shaped sternum anchors powerful flight muscles

Class Mammalia

• Approximately 4,500 species; includes rodents, bats, shrews, and moles

Key Traits

• Hair: Composed of keratin; serves for insulation and sensory purposes
• Mammary Glands: Produce milk to nourish young

Other Mammalian Features

• Endothermy: Regulate internal body temperature; supported by a four-chambered heart and diaphragm
• Placenta: In most mammals, facilitates nutrient and waste exchange between mother and developing offspring
• Specialized Teeth: Adapted to diet (e.g., carnivores vs. herbivores)
• Digestive Symbiosis: Harbor bacteria to break down cellulose in plant material
• Hooves, Horns, Antlers: Structures made of keratin or bone
• Limb Modifications: Adaptations for various modes of locomotion (e.g., flight in bats, swimming in whales)

Mammal Subclasses

• Prototheria: Egg-laying mammals (e.g., platypus, echidna)
  • Lack nipples; young lap milk from mother's fur
  • Found in Australia and New Guinea
• Theria: Viviparous (give birth to live young)
  • Marsupials: Pouched mammals with short-lived placenta (e.g., kangaroo, opossum)
  • Placental Mammals: Develop a true placenta that nourishes the embryo throughout gestation