Seed Plant Evolution

Non-Vascular Plants and Monilophytes

• These plant groups precede seed plants in evolutionary history

Seed Plants

• Classified as Gymnosperms and Angiosperms
• Exhibit vascular tissue (xylem and phloem) and a dominant sporophyte stage during their life cycle
• Characterized by seeds that facilitate embryo transport and nourishment

Sporophyte

• Diploid stage of a plant's life, producing spores via meiosis
• Dominant generation in seed plants like trees

Spore

• Haploid reproductive cell from sporophyte meiosis
• Develops into gametophytes

Gamete

• Gametophytes produce haploid sex cells (sperm/egg)
• Combine during fertilization, creating a diploid zygote, that grows into a new sporophyte

Gametophyte

• Haploid stage which generates gametes through mitosis
• Dependent on the sporophyte and highly reduced in seed plants

Adaptations of Seed Plants: Seeds

• Help plants thrive in harsh conditions
• Composed of an outer protective seed coat derived from the parent sporophyte (2n)
• Female gametophyte (1n) provides a food supply and an embryo which develops into a new plant (2n)

Adaptations of Seed Plants: Heterospory

• Involves generations with separate sexes and produces male and female gametophytes
• Gametotrophy and gamete formation occur inside male and female cones

Gymnosperm Reproductive Structures: Female Cones

• Composed of female sporophylls
• Ovules (2n) undergo meiosis, producing female spores (1n) that form a female gametophyte
• Egg nucleus (1n) develops inside the gametophyte, all retained within the female cone

Gymnosperm Reproductive Structures: Male Cones

• Stacked male sporophylls
• Male gametophyte (pollen) contains haploid tissues (1n) that create pollen grains through meiosis
• Sperm nucleus formed within each pollen grain is very small for pollination

Formation of Seeds

• Fertilized ovule develops into one
• Contains a protected developing embryo
• Seeds are released for dispersal which allows new plants to grow elsewhere, and reduces competition with the parent plant

Features of Gymnosperms

• Naked seeds that are not enclosed
• Sporophylls arranged in cones
• Seeds exposed on female sporophylls

Origin of Land Plants

• Evolved from green algae which resulted in mosses, ferns, conifers and flowering plants
• Adaptive themes for autotrophy entail offspring dispersal, light access via height, and desiccation avoidance

Key Terrestrial Adaptations

• Alternation of generations, provides walled spores for protection
• Sheltered, nurtured embryos with nutrients supplied via gametophyte

Non-Vascular Plants

• Earliest land plants lacking vascular tissues
• Major Taxon: Phylum Bryophyta
• Undergo alternation of generations with retained egg, zygote, embryo & sporophyte stages, and walled spores from the sporophyte
• Habitats are limited to moist regions and are generally not tall, this is because sperm needs water for dispersal
• Anchor to the ground with rhizoids, though do not absorb nutrients like roots

Vascular Plants

• Exhibit greater growth, energy capture, and diversification via possessing vascular tissues
• They have xylem, pholem, true roots, sporophylls

Vascular Plants: Monilophyta

• Ferns are a vascular plant group that do not have seeds
• Exhibit alternation of generational phase
• The reduced gametophyte is smaller and shorter-lived, the dominant sporophyte is larger and lives longer
• Spores can be produced (and dispersed) via wind through the sorus structure

Gymnosperms - Key Features

• Vascular with typically coned sporophylls, and seeds exposed on the female sporophylls
• Phylum Coniferophyta contains 600 species like pines and spruce, where most of them are evergreen

Gymnosperms - Cool Taxa: Yew Trees & Juniper Trees

• Yew trees have modified female cones (arils) resembling fruit
• Aril seeds are used in cancer medication production
• Juniper berries are juniper cones and are the primary gin flavoring

Angiosperms

• Vascular plants with dominant sporophyte stage
• Phylum Anthophyta is key because of the evolution of protected seeds within ovaries
• Flowers have specialized structures for sexual reproduction and comprise four rings of leaves

Flower Leaves

• Sepals
• Petals
• Stamens (male sporophylls)
• Carpels (female sporophylls)

Fruit

• A mature post-fertilization ovary
• The ovary wall (pericarp) thickens for dispersal via environmental factors (wind, water), or animal interactions (internal/external transport)

Trends in Terrestrial Plant Evolution: Reduced Water Dependence

• Pollen (gametophyte) disperses sperm without water, making water unnecessary for dispersal of sperm

Trends in Terrestrial Plant Evolution: Greater Dispersal Success

• Protection of ovules, seeds & fruits enhances dispersal

Trends in Terrestrial Plant Evolution: Greater Access to Resources

• Specialized leaves, vascular tissue, and roots enhance resource accessibility

Angiosperm Diversity

• 250,000 species have evolved in 100 million years
• Pollination and evolving species (plant/pollinator) can introduce speciation barriers
• 90% of angiosperms utilize animal pollen transfer, which increases plant and animal diversity

Co-Evolution of Seed Dispersal

• Animal/seed interactions impact angiosperm diversity
• Rodents lead to plant geographic isolation as they like specific fruits

Gametophyte vs Sporophyte: Gametophyte

• It possesses one chromosome set and generates gametes (sperm/egg) via mitosis
• Resulting sex cells are haploid which allows diploid zygotes to be formed through fertilization
• Non-vascular plants like mosses feature gametophytes as the most visible part of the plant

Gametophyte vs Sporophyte: Sporophyte

• Is a diploid structure and contains two chromosome sets
• Meiosis produces spores that grow into gametophytes
• Ferns and gymnosperms exhibit dominant sporophytes

Spores vs. Gametes

• These can be confused so understanding key differences is essential
• Spores are haploid reproductive cells that grow into a gametophyte
• They are derived from sporophyte meiosis
• Haploid gametes fuse with another gamete (sperm + egg) and produce zygotes that grow into a sporophyte
• Mitosis in the gametophyte stage produces gametes

Life Cycle Alternation

• Sporophytes generate spores by meiosis
• Spores grow into gametophytes
• Gametophytes which create gametes by mitosis
• Gametes unite in fertilization which creates new sporophyte generations

Features of Fungi: Structure

• These are uni/multicellular eukaryotes
• Found across aquatic and land ecosystems
• Cell walls consist of polysaccharide chitin

Features of Fungi: Nutrition

• Fungi are heterotrophs that are fundamental to ecosytem nutrient recycling
• They are saprobes because they get nutrients from breaking down matter
• Complex molecules break down through excreted digestive enzymes, and those products are absorbed

Features of Fungi: Structure of Multicellular Fungi

• Filament cells surrounded by a cell wall, called a hyphae compose multicellular fungi
• Septate hyphae exhibit visible divisions, in comparison to aseptate hyphae which are a continuous cytoplasmic mass

Features of Fungi: Mycelium Structure

• This consist of a mass of hyphae and maximizes surface area for nutrient absorption
• Found in fungus roots and across its body

Adaptive Themes: Stationary Heterotrophy (Saprobes)

• Fungi depend on a substrate to extend hyphae across and absorb nutrients using externally secreted enzymes
• In stable conditions they reproduce asexually but under uncertain or changing conditions they asexually reproduce

Unicellular Fungi, Symbioses, & Lifecycle of Fungi

• Unicellular fungi lifestyle is similar to protists
• Fungi interact with other organisms through parasitism and symbiosis
• The fungal lifecycle includes haploid spores that germinate and disperse into a mycelium
• Reproductive Pathways: Asexual with haploid production, Sexual with fertilization and meiosis

Fungal Diversification

• Zygomycota include mold, parasites, and symbionts which possess aseptate mycelia and efficient spore dispersal
• Ascomycota possess ascocarp fruiting bodies, septate hyphae, and mutualistic symbiosis with algae or cyanobacteria
• Lichens form mutualistic relationships with photosynthetic organisms, providing protection for moisture and mineral trapping
• The photosynthetic organism generates organic carbon, and new habitats can be exploited

Basidiomycota

• A club fungi phylum: includes molds, bracket fungi, mushrooms, lichens, and mycorrhizae
• Decomposers, exhibit mutualistic symbiosis with "farming" ants, basidium- specialized hyphae, and fruiting bodies and septate hyphae

Animal Key Features

• Heterotrophs with internal digestion, eukaryotic and multicellular
• Note: animal cell walls are not present (in comparison to plant/fungi)
• Plants lack cellulose cell walls and are autotrophs, animals are heterotrophs lacking these
• Fungi digest and absorb nutrients externally and include chitin cell walls, animals lack cell walls as well and digest internally
• Animal are classified into 30-35 phyla via structure and development relating to body plans

Animal Adaptive Themes

• Mobile heterotrophy to identify food and diversify feeding strategies
• Maximize efficiency through decreasing energy spent to allocate energy to reproduction

Animal Body Plans

• Asymmetry: No symmetry (e.g. sponges)
• Radial symmetry: Infinite planes of symmetry (e.g. sea anemones)
• Bilateral symmetry: Single plane of symmetry with a cephalization (e.g. animals with heads)

Animal Tissues

• Absent: (e.g. sponges)
• Diploblastic: Two embryonic tissue layers
• Triploblastic: Three embryonic tissue layers
• In coelomates, a fluid filled space resides between the gut/body wall protects, circulates, and acts as a skeleton for animals without one

Protostomes vs. Deuterostomes Development

• The difference between the three lies in if it is a three layered structure, whether the anus or mouth develops first
• Protostomes start with the mouth
• Deuterostomes start with the anus

Animal Basic Life Cycle

• Zygote to embryo to diploid adult life cycle including meiosis and fertilization

Life Cycle Variations: Sperm Delivery and Egg Handling

• Sperm can be broadcast or packaged
• Eggs handled through broadcast, live birth, or external brooding, showing varying degrees of parental care
• Development pathways can also be direct(no intermediate larval stages) or indirect (includes larval stages)

Life Cycle Variations: Gonad Types

• Separate or hermaphrodites

Anemones, Corals, Jellyfish

• Members of Phylum Cnidaria featuring Body Plans with radial symmetry and diploblastic tissues
• They are neither deuterostomes nor protostomes, possessing a sac-like body with one opening for both digestion and waste
• They are either Medusa (bell-like shape with downward facing mouth) or Polyp (cylindrical shape with upward facing mouth)

Anemones, Corals, Jellyfish: Reproduction

• Asexual polyp reproduces colonies via budding
• Sexual medusa reproduces waterborne larvae (planulae) by individuals that release gametes into the water for fertlization

Anemones, Corals, Jellyfish: Diversity & Adaptation

• Diversity includes class Cubozoa (Medusa only), Anthozoa (Polyp only forms, like corals and sea anemones), and Scyphozoa, which contains jellyfish that only exist as medusa
• Coloniality adapts polyps to asexually form colonies exhibit divisions of labor for improved efficiency & survival

Mollusks

• Phylum Mollusca features around 93,000 snails, squids, clams and slugs that have a bilateral symmetry that makes them triploblastic coelomates
• These complete digestive systems contain a one way gut with shells for protection
• Radulas grasp food with teeth ribbons, muscles in the foot structure enable movement, and the mantle cavity facilitates gas exchange (gills) and capturing of food

Mollusks: Classes

• Polyplacophora are marine grazers with shells divided into 8 plates
• Gastropoda possess mantle cavities at the head that are either snails (with shells) or slugs (without shells)
• Bivalvia clams use modified gills for suspension feeding and has shells that fully enclose the body.
• Cephalopoda are evolved predators (squid) with tentacles for grasping prey and movement via jet propulsion siphon.

Phylum Arthropoda: Basic Information

• Exhibits 1.1 million species across terrestrial, marine, and freshwater
• Triploblastic coelomates that undergo protostome development
• Exhibit body segmentation, joints, and digestive/nervous/circulatory systems

Phylum Arthropoda: Key Features

• Has segmentation, exoskeleton, jointed appendages
• The exoskeleton allows movement, protection and consist of a hardened cuticle secreted outside the skin, and contains fine sensory hairs (setae)

Phylum Arthropoda: Molting and Diversity

• Arthropods molt to grow through cuticle softening and seam breaking
• Cuticle breaks, new cuticle is stretched, and hardens
• Segmentation number/fusion and specialized appendages means arthropods adapted to every Earth environment

Echinoderms

• Triploblastic coelomates, exhibit pentaradial symmetry as adults/bilateral ancestors, all classified as deuterostomes
• Internal anatomies include a distributed nervous system, one way gut, and water vascular system (hydraulic for locomotion and feeding)

Echinoderms: Adaptations

• Ossicles flexibility leads to strength in calcium carbonate structures
• Neural control over tissues aid ligament movement

Chordates: Basic Information

• Chordates (50,000 marine, terrestrial, freshwater species) exhibit a one way gut, triploblastic organization
• Exhibits bilateral symmetry and are deuterostomes

Chordates: Four Defining Features

• Muscular tail extends past the anus while the pharynx has slits to allow exit of water
• The dorsal hollow nerve cord (a nervous system component) differs from the ventral one in other species
• Notochord is a flexible rod that provides skeletal components and spinal discs in humans

Chordates: Diversity, Fish, and Vertebrata

• Cephalochordata subphylum resemble primary chordate body plans but pump water to filter food particles via suspension feeding
• Vertebrate subphylum retain tetrapod features, and the modified cranium is used to protect brains
• Vertebrata skeletons, made to protect the nerve chord of the derived muscles are often modified

Fish: Cartilaginous and Ray finned

• Cartilaginous fishes like rays and sharks have jaws, and skeletons are cartilage-based
• Ray finned fishes are bone mineralized and exhibit all the typical vertebrate traits

Human Interaction: Overfishing

• Fisheries face potential collapse due to catch drops
• Declining biodiversity and threatening food sources, extinction level event may occur by 2050 so as 10% of fisheries remaining

Fish Locomotion and Sarcopterygii Adaptations

• Thrust against water helps fish propel forward with their bodies, fins and tails
• Lobe finned ancestors of tetrapods evolved land movement survival
• Living today are lobed finned fishes

Tetrapods: Classification

• Evolved from fins of lobed finned fish
• Face challenges such as land propulsion, desiccation prevention, temperature regulation, oxygen extraction, and gravity overcoming

Tetrapods: Adaptations

• 4 Limbs support land movement
• Backbone and pelvic girdle support limbs
• Breathing achieved through developed lungs
• Gill slits utilized into adult jaws and ears

Amphibians

• An example of that include salamanders, frogs, and newts
• Live partial aquatic lives where scaly skin is used for lung respiration, which can face drying out, while eggs face drying out as well and require aquatic environments for survival

Amphibian Tetrapod Adaptations and Human Interaction

• Tetrapods develop miniature adult hatches or aquatic larvae metamorphosing into adults
• Parental care ranges from some to none at all
• 1/3 exhibit extinction as pollutant, fungal disease, and habitat/climate changes threaten their existence
• Wetland habitat protects amphibians and ensures their survival

Reptiles

• Birds, lizards, crocodiles, snakes, turtles and dinosaurs
• Prefer predominantly terrestrial habitants, while others live aquatically
• Amniotic eggs containing shells protect against desiccation and require internal fertilization so extra embryonic membranes assist in embryo protection and nourishment
• Lungs and scales prevent against water loss which make scales and lungs key to reptile evolution

Reptilian Adaptations and Bird Classification

• Most give birth or lay eggs, but are either ectothermic (absorb environment body heat) or endothermic (generate body heat internally)
• Birds are now categorized as a part of reptilian groups, of which have a diverse feeding niche as the most are capable of flight and reduce weight

Birds' Evolution & Features

• Evolved feathers/scales
• Amniotic eggs mean links to reptilian relatives, adaptions allows high metabolism for flight through unique feather shapes and different forms.

Birds' bills and traits

• Adapted bill and specialized feet claws for varying diets
• For weight saving, some traits include single ovary, no bladder, and hollow wings

Bird Human interaction

• Protected species will impact others

Mammalian characteristics

• Nourishment to young through a milk production structure
• Fur/Hair used for body insulation
• Endothermic to regulate the internal body temperature
• Placenta for birth while monotremes lay eggs

Mammalian Diversity

• Monotremes lack nipples but lay eggs and milk comes from the skin
• Short pregnancies come from marsupials when underdeveloped offspring finishes develop in a pouch
• Complex placenta, developed in uterus with lives births are features for placental mammals

Mammalian & Eutherian and Behaviour Convergence

• Herbivores and predators adapt radiation similar continents
• Innate genetically programmed subjected behaviour
• Learn inherit to adapt and responses
• Cultural passed through generation like whale songs or lactase tolerance through milk