Plant Evolution and Life Cycles

Plants and the Conquest of Land

• Plants evolved from green algal ancestors called streptophyte algae
• Adaptations for terrestrial life include: structural support, reproduction without water, and water retention mechanisms

Evolutionary Origin

• Kingdom Plantae organisms are multicellular, eukaryotic, and plastid-containing, living mostly on land
• Closest relatives to plants are Charophycean (streptophyte) algae
• Shared traits with Charophycean algae include: plasmodesmata, similar cytokinesis, and egg/sperm reproduction

Plant Life Cycles

• Zygotic life cycle (algae): Dominant haploid phase where the zygote is the only diploid stage
• Sporic life cycle (land plants): Alternates between multicellular diploid sporophyte and haploid gametophyte
• Sporophyte (2n): Produces haploid spores by meiosis
• Gametophyte (1n): Produces gametes by mitosis

Reproductive Adaptations

• Protect gametes using Gametangia
• Antheridia: produce sperm
• Archegonia: produce eggs
• Zygote develops into an embryo protected by maternal tissues, using placental transfer tissue

Major Plant Groups (9 Phyla)

• Liverworts – Hepatophyta
• Mosses - Bryophyta
• Hornworts – Anthocerophyta
• Lycophytes – Lycophyta
• Pteridophytes – Pteridophyta
• Cycads - Cycadophyta
• Ginkgos – Ginkgophyta
• Conifers – Coniferophyta
• Angiosperms (flowering plants) – Anthophyta

BRYOPHYTES (Non-Vascular Plants)

• Includes mosses, liverworts, and hornworts.
• Lack vascular tissue
• Dominant gametophyte
• Flagellated sperm require water for reproduction
• Rhizoids act as roots
• Grow in moist environments

SEEDLESS VASCULAR PLANTS

Lycophytes

• Small, ancient group with microphylls (small leaves)
• Sporangia are present on leaves
• Some formed tall trees in the Carboniferous period

Pteridophytes

• Includes ferns, horsetails, and whisk ferns
• Dominant sporophyte
• Has vascular tissue
• Sori (clusters of sporangia) are on frond undersides

GYMNOSPERMS

• Have "naked seed" plants (no fruit covering)
• Dominant in the Mesozoic era
• Pollen is used for fertilization rather than water
• Ovules become seeds after fertilization
• Seed makeup: embryo + nutritive tissue + seed coat

Gymnosperm Phyla

• Cycadophyta: tropical, palm-like with large cones
• Ginkgophyta: has only one extant species (Ginkgo biloba)
• Coniferophyta: pines, firs; they produce cones and needles
• Gnetophyta: unique among gymnosperms

Seed Advantages

• Protection and food for embryo
• Dormancy and dispersal abilities
• Reproduction without water
• Endosporic gametophytes (grow within spore walls)

ANGIOSPERMS

• Flowers are specialized for reproduction
• Fruits develop from ovaries, protect and aid in seed dispersal
• Endosperm is nutritive tissue formed by double fertilization
• Co-evolve with pollinators

Monocots vs. Eudicots

• Cotyledons: Monocots have 1, Eudicots have 2
• Leaf veins: Monocots have parallel veins, Eudicots have net-like veins
• Vascular tissue: Monocots have scattered tissue, Eudicots have ring-like tissue
• Examples: Monocots include grasses and lilies, Eudicots include roses and beans

ANIMAL DIVERSITY

• Animals are multicellular, eukaryotic, heterotrophs
• They have no cell walls
• They are motile at some stage
• Most reproduce sexually
• Originated from choanoflagellate-like protists

Characteristics of Animals

• Have Tissues: Ectoderm, endoderm, and mesoderm (triploblastic)
• Have nervous & muscle tissue
• Have an Extracellular matrix for structural support
• Have Cell junctions for anchoring, tight and gap functions
• Modes of feeding: Suspension feeding, bulk feeding, and fluid feeding
• Muscle + nervous system enable movement for food, mates, and escape
• Reproduction & Development
• Fertilization is internal or external
• Zygote develops via cleavage → blastula → gastrula
• Metamorphosis can occur (e.g., tadpoles → frogs)

Evolutionary Timeline

• Proterozoic eon was when first multicellular animals appeared
• Cambrian explosion (533-525 mya) caused major diversification
• Burgess Shale is an important fossil site

Body Plan Traits

• Tissue Layers:
  • Diploblastic animals have 2 layers (ecto + endoderm), e.g., cnidarians
  • Triploblastic animals have 3 layers (+ mesoderm), e.g., most animals
• Symmetry:
  • Radial symmetry: Around a central axis, e.g., jellyfish
  • Bilateral symmetry: Left-right symmetry enables cephalization, e.g., most animals
• Body Cavities:
  • Acoelomate: No cavity, e.g., flatworms
  • Pseudocoelomate: Incomplete cavity, e.g., nematodes
  • Coelomate: Fully lined with mesoderm, e.g., vertebrates

Introduction to Animal Diversity

• Tissue layers: Diploblastic (2 layers) vs. Triploblastic (3 layers)
• Symmetry: Radial vs. Bilateral
• Body cavities: Acoelomate, Pseudocoelomate, and Coelomate
• Embryological development: Protostomes and Deuterostomes
• Segmentation: Supports complex movement
• Molecular data preferred over morphological traits
• Molecular phylogenetics is more accurate for understanding evolutionary relationships

Major Animal Phyla Overview

Ctenophora (Comb Jellies)

• Marine, bioluminescent, ~100 species
• First with complete gut (mouth → gut → 2 anal pores)
• Have 8 rows of cilia for movement, but no stinging cells
• Hermaphroditic

Porifera (Sponges)

• Asymmetrical
• No true tissues or organs
• Sessile adults, motile larvae
• Filter feeders that use choanocytes
• Reproduce sexually (hermaphrodites) and asexually (budding)

Cnidaria (Jellies, Corals, Anemones)

• Radial symmetry
• True tissues
• Gastrovascular cavity (one opening)
• Two body forms: Polyp (sessile) and Medusa (motile)
• Tentacles with nematocysts (stinging cells)

Lophotrochozoa

• Named for lophophore or trochophore larva
• Includes:
  • Platyhelminthes: Acoelomate, 3 tissue layers, free-living/parasitic
  • Rotifera: Microscopic with a ciliated corona
  • Bryozoa & Brachiopoda: Lophophore, true coelom
  • Mollusca: Soft-bodied with mantle, radula, and varied shells
    • Has Gastropoda, Bivalvia, and Cephalopoda
  • Annelida: Segmented worms

Ecdysozoa

• Named for ecdysis (molting of cuticle)
• Includes:
  • Nematoda: Roundworms, pseudocoelomates, many parasitic
  • Arthropoda: Most diverse; exoskeleton, segmented body, jointed limbs
    • Subphyla: Chelicerata, Myriapoda, Crustacea, and Hexapoda

Deuterostomes

• Echinodermata (Sea Stars, Urchins, Cucumbers)
  • Echinodermata adults have radial symmetry, while larvae have bilateral symmetry
  • No cephalization or brain
  • Has an endoskeleton, water vascular system, and tube feet
  • Capable of autotomy Classes:
  • Asteroidea: Predatory
  • Ophiuroidea: Filter feeders
  • Echinoidea: No arms
  • Crinoidea: Filter feeders, stalked
  • Holothuroidea: No arms, reduced skeleton

Chordata (Includes Vertebrates and Some Invertebrates)

• Has; Notochord, Dorsal hollow nerve cord, Pharyngeal slits, and Post-anal tail
• Invertebrate chordates include: Urochordata and Cephalochordata
• Vertebrates evolved via Hox gene duplications

Vertebrate Clades

• Cyclostomata: Jawless
• Chondrichthyes: Cartilaginous
• Actinopterygii: Ossified skeleton
• Sarcopterygii: Fleshy fins
• Amphibia: Moist skin, metamorphosis
• Testudines: Hard shell
• Squamata: Scaled skin
• Crocodilia: 4-chambered heart
• Aves: Feathers, hollow bones
• Mammalia: Hair, milk

Sarcopterygii

• Has fleshy, lobed fins supported by bones and muscles
• Evolutionary link between fish and land-dwelling tetrapods
• Transitional Taxon: Tiktaalik rosae
• Broad skull, eyes on top, lungs, and pectoral fins with finger-like bones, 370 million years ago

Early Tetrapods and Amphibians

• Adaptations for Land Life: Strong vertebral column, girdles braced against backbone, sturdy, limb-like fins, lungs and nostrils, and sensory system modifications
• Amphibia Includes: Frogs, toads, salamanders, caecilians

Amphibians

• General Traits: Mostly small, carnivorous adults
• Aquatic larvae are often herbivorous
• Metamorphosis: Tadpole → Adult Groups:
  • Anura: Frogs & toads
  • Urodela: Salamanders & newts
  • Gymnophiona: Caecilians Adaptations:
  • External fertilization
  • Buccal pumping for lungs
  • Oxygen-absorbing skin
  • 3-chambered heart

Amniotes

• Amniotic egg
• Shell types: - Hard (birds) - Leathery (reptiles) - Absent (mammals)
• Other Traits: Keratinized skin, Thoracic breathing, Water-conserving kidneys, and Internal fertilization
• Reptiles and Birds: Birds are now classified within reptiles
• Extinct clades: Dinosaurs, pterosaurs, and ichthyosaurs
• Birds: Feathers, hollow bones, air sacs, reduced organs and are endothermic; 4-chambered heart

Mammals

• Originated 225 mya Traits:
  • Hair, mammary glands
  • Specialized teeth, large braincase
  • Single jawbone, 3 ear bones, external ears

Mammal Subclasses:

• Prototheria: egg-laying, no placenta
• Metatheria: pouch development
• Eutheria: long gestation

Plant Phyla

• Nonvascular (Bryophytes): Liverworts, Mosses, Hornworts
• Seedless Vascular: Lycophytes, Pteridophytes
• Seed Plants: - Gymnosperms: Cycads, Ginkgos, Conifers - Angiosperms: Anthophyta

Life Cycles

• Zygotic (Algae): Haploid dominant
• Sporic (Plants): Alternation of generations
• Shift toward sporophyte dominance in plant evolution

Seed Evolution

• Homosporous vs. Heterosporous
• Endosporous Development: Gametophytes develop inside spore wall for protection
• Seeds have crucial for dispersal and terrestrial life

Gymnosperms vs Angiosperms

• Gymnosperms: - Pollen grains with nonmotile sperm - Ovules → Seeds upon fertilization - No water needed for fertilization
• Angiosperms: Flowers & fruits with unique triploid tissue

Animal Evolution and Key Innovations

• Animals are defined by being Multicellular heterotrophs with no cell walls and motility
• Closest relative: Choanoflagellates

Innovations

• Tissues: Diploblastic (2 layers) vs Triploblastic (3 layers)
• Symmetry: Radial vs Bilateral
• Body Cavities: Acoelomate vs Pseudocoelomate vs Coelomate
• Embryonic Development: Protostomes vs Deuterostomes
• Segmentation allows for specialization

Deuterostomia

• Includes: Echinoderms, Chordates

Echinoderms:

• Adults have Radial symmetry, while larvae are bilateral
• Have a water vascular system and endoskeleton
• Lack an excretory system

Chordate Features

• Notochord
• Dorsal hollow nerve cord
• Pharyngeal slits
• Post-anal tail
• Invertebrate chordates: Urochordata (tunicates) and Cephalochordata (lancelets)
• Vertebrates evolved via Hox gene duplications

Vertebrate Clades:

• Jawless Cyclostomata
• Cartilaginous Chondrichthyes
• Ossified skeleton Actinopterygii
• Fleshy fins Sarcopterygii
• Moist skin Amphibia
• Hard shell Testudines
• Scaled skin Squamata
• 4-chambered heart Crocodilia
• Feathers Aves
• Hair Mammalia

Animal Organization

• There is Organization of animal bodies
• There are Structure-function relationships
• There are Homeostasis principles

Cellular and Tissue Organization

• Animal cells exchange materials, obtain energy, respond to signals, synthesize molecules via reproduction
• Animals develop from a single fertilized egg → specialized cells → tissues → organs → organ systems

Animal Tissues

• Muscle Tissue: Contracts to produce movement - Skeletal muscle = voluntary - Smooth muscle = involuntary - Cardiac muscle = involuntary
• Nervous Tissue: Neurons and glia for signal processing and communication
• Epithelial Tissue: Sheets that line surfaces Layers: simple, stratified, pseudostratified, transitional Functions: protection, absorption, and secretion
• Connective Tissue: Structure & support

Organs and Systems

• Organs has ≥2 tissues working together
• Organ systems have integrated organs for shared functions
• Hox genes regulate body layout and organ development

Structure-Function Relationship

• Similar structures often suggest similar functions
• Higher surface area-to-volume ratio allows for efficient diffusion

Homeostasis

• Involves maintaining stable internal conditions despite external change
• Blood glucose levels fluctuate but return to normal via homeostatic mechanisms

Homeostatic Regulation & Fluids

• Understanding how internal states are regulated
• Homeostatic Control Systems
  • Set point: Desired/normal value
  • Sensor: Detects deviations
  • Integrator: Compares to set point
  • Effector: Makes adjustment
  • Homeostatic feedback restores equilibrium

Feedback Mechanisms

• Negative Feedback: Restores equilibrium
• Positive Feedback: Amplifies change
• Feedforward Regulation: Anticipates change

Chemical Signaling:

• Paracrine and Neurotransmitters are local signals, wheras Hormones are long distance signals

Fluid Compartments:

• Fluid located Intracellular or Extracellular
• Closed systems in verebrates, mixed in invertebrates
  • Compartmentalization allows specialization

Solute & Water Transport

• Passive transport: Simple diffusion, Facilitated diffusion
• Water moves via osmosis

Osmotic Challenges

• Crenation: Cell shrinkage
• Hemolysis: Cell swelling and bursting
• Result from exposure to abnormal solute concentrations

Water/lon Balance

• Essential for survival and enzyme function
• Regulated via:
  • Osmoregulation
  • Obligatory exchanges
  • gain water, must conserve salts

Osmoregulation

• Osmoregulators: Maintain constant internal osmolarity
• Osmoconformers: Match body osmolarity to environment