Plant Transport Mechanisms

Plant Transport

• Plants use three routes for water and nutrient transport to the root vascular tissue: apoplast, symplast, and transmembrane.

Apoplast Route

• Water moves through cell walls and intercellular spaces, not entering the cells.

Symplast Route

• Water enters the cytoplasm of cells and moves through plasmodesmata, connecting adjacent cells.

Transmembrane Route

• Water crosses plasma membranes multiple times, entering and exiting cells.

Water Movement

• Water moves from the soil through plants to the atmosphere due to physical forces.
• Water is absorbed by roots, moves up the xylem, and exits through the leaves into the atmosphere.
• The cohesion-tension theory explains water movement up the xylem: transpiration pull, cohesion, and adhesion.
• Transpiration pull is the evaporation of water from leaves, creating a negative pressure (tension) in the xylem.
• Cohesion is the attraction between water molecules, and adhesion is the attraction between water molecules and xylem walls.
• These forces work together to pull water up the plant.

Stomata

• Stomata open and close to regulate gas exchange and water loss.
• Guard cells control stomata opening and closing.
• Environmental conditions like light, carbon dioxide concentration, and water availability trigger stomatal events.

Translocation

• Translocation is the movement of organic compounds, primarily sugars, through the phloem.
• Substances are translocated from sources (photosynthesizing leaves, storage tissues) to sinks (actively growing tissues, roots, fruits).
• Translocation delivers sugars where the plant needs them.

Pholem Cells

• Sieve-tube elements and companion cells are the primary cells involved in translocation.
• Sugars are actively transported into sieve-tube elements at the source, increasing solute concentration.
• Water enters the sieve-tube elements due to osmosis, creating pressure that pushes the sugars to the sink.
• At the sink, sugars are unloaded, and water exits the phloem.

Xylem vs Phloem

• Xylem transports water and minerals from roots to leaves; phloem transports sugars and organic compounds throughout the plant.
• Xylem transport is unidirectional (upward); phloem transport is bidirectional (source to sink).
• Xylem involves dead cells; phloem involves living cells (sieve-tube elements and companion cells).
• Xylem transport is driven by transpiration pull (negative pressure); phloem transport is driven by pressure flow (positive pressure).

Plant Reproduction

• Angiosperms are flowering plants.
• Key flower parts include sepals, petals, stamens (anthers and filaments), and carpels/pistils (stigma, style, and ovary).
• Sepals protect the flower bud, petals attract pollinators, stamens produce pollen, and carpels contain the ovules.

Pollination

• Pollination is the transfer of pollen from the anther to the stigma.
• Self-pollination is pollen transfer within the same flower or plant; cross-pollination is pollen transfer between different plants.
• Pollen tube growth is required for fertilization.

Flower Trends

• Over evolutionary time, flower structure and pollination mechanisms have trended towards reduction and specialization.
• Wind pollination relies on air currents; animal-assisted pollination is facilitated by animals like bees.

Self-Pollination

• Self-pollination advantages: reproductive assurance, especially in the absence of pollinators.
• Self-pollination disadvantages: reduces genetic diversity, increasing the risk of inheriting harmful traits.
• Self-incompatibility genes prevent pollen germination on the same plant, promoting outcrossing.
• Outcrossing is reproduction involving pollen from different plants, increasing genetic diversity.

Asexual Reproduction

• Asexual reproduction mechanisms include vegetative propagation, apomixis, and fragmentation.
• Vegetative propagation: new plants grow from stems, roots, or leaves.
• Apomixis: seed formation without fertilization.
• Fragmentation: parent plant breaks into parts that develop into new plants.
• Asexual reproduction advantages: rapid reproduction, especially in stable environments.
• Asexual reproduction disadvantages: lack of genetic diversity, reduced adaptability to changing environments.

Agriculture and Industry of Plants

• Asexual reproduction is used to produce genetically identical plants with desirable traits in agriculture and industry.
• Examples include using cuttings, grafting, and tissue culture.
• Vernalization: cold exposure is required for flowering initiation.
• Photoperiod: light duration influences flowering timing.
• Florigen: hormone signaling plant to initiate flowering.
• Autonomous pathway: flowering occurs independently of environmental clues.

Introduction to Animals

• Animals are eukaryotic, multicellular, heterotrophic organisms.
• Heterotrophic nutrition is obtained through ingestive feeding.
• Animals have unique cell types like nerve and muscle cells.
• Animals are characterized by the presence of an extracellular matrix (collagen).
• Embryonic layers (tissues) are developed from three primary germ layers.

Animal Evolution

• Shared derived traits of animals include: multicellularity, heterotrophic nutrition, extracellular matrix, unique cell types, and embryonic layers.
• Shared ancestral traits include: eukaryotic cells and sexual reproduction.

Animal Body Plans

• Body plan features: presence of tissues, body symmetry, early embryonic development, presence and type of body cavity, and segmentation.
• Presence of tissues: Parazoa (e.g., Porifera) lack true tissues; Eumetazoa have true tissues.
• Body symmetry: asymmetry (Porifera), radial symmetry (Cnidaria), bilateral symmetry (Bilateria).
• Early embryonic development: protostomes (mouth develops from blastopore), deuterostomes (anus develops from blastopore).
• Body cavity: acoelomates (no body cavity), pseudocoelomates (partially lined body cavity), coelomates (true body cavity fully lined with mesoderm).

Phylogenetic Tree of Metazoa

• Metazoa includes: Porifera, Cnidaria, Platyhelminthes, Annelida, Mollusca, Nematoda, Arthropoda, Echinodermata, and Chordata.
• Rooted with the Choanoflagellates as an outgroup.
• Divided into Protosome vs Deuterostome and Lophotrochozoa vs Ecdysozoa.
• Acoelomates: no body cavity; e.g., Platyhelminthes.
• Pseudocoelomates: partially lined body cavity; e.g., Nematoda.
• Coelomates: true body cavity fully lined with mesoderm. The phylogenetic tree illustrates evolutionary relationships among animal phyla.

Colonial Flagellate Hypothesis

• Multicellular animals evolved from colonial protists.
• Molecular evidence: Choanoflagellates are closest relatives to animals.

Human Evolution

• Human taxonomy: Eukarya, Animalia, Chordata, Mammalia, Primates.
• Humans share characteristics with other mammals and apes.
• Humans are distinguished by bipedalism, larger brain, complex language, and tool use.

Animal Development

• Events for fertilization: sperm activation, acrosomal reaction, membrane fusion, egg activation, and nuclear fusion.
• Polyspermy is blocked by both a fast block (electrical barrier) and a slow block (cortical reaction).
• Terms: cleavage (initial cell divisions post-fertilization), blastula (hollow ball of cells surrounding blastocoel).
• Holoblastic is complete cleavage in eggs with little/moderate yolk.
• Meroblastic is incomplete cleavage in eggs with large yolk.
• Gastrulation forms three germ layers: ectoderm, mesoderm, and endoderm.
• Mechanisms: invagination, involution, and epiboly.

Organ Development

• Ectoderm develops into skin and nervous system.
• Mesoderm forms muscles, bones, and organs.
• Endoderm gives rise to digestive and respiratory systems.

Polyspermy

• Fast block: electrical barrier preventing additional sperm binding.
• Slow block: cortical reaction creating a physical barrier post-fertilization.

Blastula and Gastrulation

• Blastula is the hollow ball of cells surrounding a fluid-filled cavity.
• Blastocoel is the fluid-filled cavity within the blastula.
• Polyspermy prevention: mechanisms to block multiple sperm fertilizing an egg.

Structures Formed

• Zygote is the diploid cell resulting from fertilization.
• Archenteron is the structure formed during gastrulation developing into digestive tube.
• Hensen's node is the site of cell migration in bird gastrulation.
• Primitive streak is the area where cells migrate during gastrulation in birds and mammals.

Germ Layers

• Superficial cleavage: nuclei divide within common cytoplasm before cellularization.
• Radial cleavage: type of cleavage with symmetrical cell division.
• Unequal cleavage: cell sizes differ due to yolk distribution.

Amniotes and Non-Amniotes

• Amniotes: reptiles, birds, and mammals with extraembryonic membranes.
• Non-amniotes: amphibians and fish lacking amnion and chorion.

Animal Development Processes

• Organogenesis: germ layers differentiate into specific organs.
• Salivary gland development: involves ectodermal cell invagination and duct formation.
• Neurulation: formation of neural tube from ectoderm thickening.
• Cell movement: essential for morphogenesis and tissue organization.
• Apoptosis: programmed cell death shaping organs and structures.

Induction

• The Spemann and Mangold experiment: transplanting tissue creates second nervous system.
• Primary induction: organizer signals ectoderm to form the neural plate.
• Secondary induction: optic vesicle signals lens placode for eye development.

Body Temperature

• Endotherms generate internal heat through metabolic processes to regulate body temperature.
• Ectotherms depend on external heat sources for temperature regulation.
• Poikilotherms allow their body temperature to vary with environmental conditions.
• Homeotherms maintain a constant body temperature despite external changes.
• Heterothermic organisms switch between ectothermic and endothermic states.

Heat Transfer Mechanisms

• Include conduction, convection, radiation, and evaporation.
• Mechanisms: behavioral adjustments for optimal heat regulation.

Thermoregulation in Ectotherms and Endotherms

• Ectotherm strategies: behavioral adjustments for optimal heat regulation.
• Endotherm strategies: insulation (fur, feathers), circulatory adaptations, evaporative heat loss, metabolic adjustment.

Homeostasis

• Involves sensors, control centers, and effectors
• Feedback control mechanisms like negative and positive feedback are crucial for stability.
• Negative feedback counteracts stimulus to maintain balance.
• Positive feedback amplifies stimulus for specific outcomes.

Respiratory System

• Exchange depends on area, pressure, thickness (Fick's Law).
• Gas exchange increases efficiency with large area.
• Thin respiratory surfaces have minimized distance for faster gas diffusion.
• Concentration gradients are maintained by ventilation and countercurrent exchange.

Gills

• Functions via water flowing allowing O2 diffusion into blood.
• The advantages include large area and efficient gas exchange.
• Disadvantages: inefficient in air; can collapse and dry out.

Respiratory System Types

• Tracheal systems: direct oxygen delivery in small-bodied animals.
• Cutaneous respiration: gas exchange through moist skin.
• Frog lungs: simple sac-like lungs with low efficency.
• Bird lungs: rigid lungs with air sacs for continuous flow.
• Mammal lungs: highly branched, alveolar lungs for moderate efficiency.

Circulatory System

• Open: hemolymph pumped into open spaces.
• Closed: blood confined to vessels.
• Multi-chambered heart: evolutionary adaptation for efficient blood circulation.
• Fish heart structure: 2 chambers with simple circulation.
• Amphibian heart structure: 3 chambers with partial separation of blood.
• Birds and mammals heart structure: 4 chambers for complete blood separation.
• Double circulation: Separate circuits for pulmonary and systemic blood flow.

Plant Tissues

• Dermal tissue is the outer protective layer against environmental stressors.
• The epidermis is the first line of defense for plants.
• The cuticle is a waxy layer preventing water loss.
• Guard cells regulate stomata for gas exchange.
• Stomata are pores for gas exchange in plants.
• Trichomes are hair-like structures for protection and water retention.
• Root hairs increase surface area for nutrient absorption.
• Ground tissue is involved in storage, photosynthesis, and repair.
• Parenchyma are thin-walled cells for storage and photosynthesis.
• Collenchyma cells provide flexible support in young stems.
• Sclerenchyma are rigid support cells with thick, lignified walls.
• Vascular tissue conducts water, nutrients, and sugars in plants.
• Xylem transports water and minerals from roots to leaves.
• Phloem transports sugars and organic compounds throughout plants.
• Meristematic tissue is comprised of undifferentiated cells for growth and regeneration.
• The apical meristem is responsible for primary growth at tips of roots.
• The lateral meristem facilitates secondary growth along stems and roots.
• The intercalary meristem is regrowth tissue located at grass nodes.

Key Processes

• Transpiration pull is water evaporation creating negative pressure in xylem.
• Environmental triggers are factors influencing stomata opening and closing.
• Sources are photosynthesizing leaves and storage tissues.
• Sinks are actively growing tissues like roots and fruits.

Flower Anatomy

• Sepals protect the flower bud before it opens.
• Petals attract pollinators with color and scent.
• Stamens are male reproductive organs producing pollen.
• Anthers are part of stamen that produces pollen.
• Filaments support anthers in stamen structure.
• Carpels/pistils are female reproductive organs of the flower.
• The stigma captures pollen during pollination.
• The style connects stigma to ovary in carpels.
• The ovary contains ovules in female reproductive structure.

Genetic Diversity

• Genetic diversity refers to a variety of genes within a population.
• Self-incompatibility genes prevent pollen germination on the same plant.
• Outcrossing is reproduction involving pollen from different plants.

Plant Processes

• Vernalization is cold exposure required for flowering initiation.
• Photoperiod is light duration influencing flowering timing.
• Florigen is a hormone signaling plant to initiate flowering.
• The autonomous pathway: flowering occurs independently of environmental cues.

Embryonic Development Terms

• Cleavage stage refers to initial cell divisions post-fertilization.
• The blastula stage is a hollow ball of cells surrounding blastocoel.
• The gastrula stage refers to the formation of germ layers from blastula.

Animal Development Processes

• Sperm activation is when a sperm interacts with egg's protective layers.
• The acrosomal reaction is when sperm enzymes digest egg's protective layers.
• Membrane fusion is when sperm and egg membranes combine for fertilization.
• Egg activation is when calcium release triggers metabolic changes in egg.
• Nuclear fusion is when sperm and egg nuclei combine to form zygote.
• The fast block to polyspermy is an electrical barrier preventing additional sperm entry.
• The slow block to polyspermy is the cortical reaction modifying egg's outer layer.
• Blastomeres are smaller cells formed during cleavage.
• Holoblastic cleavage is complete cleavage in eggs with little/moderate yolk.
• Meroblastic cleavage is incomplete cleavage in eggs with large yolk.
• Gastrulation is a process forming three germ layers: ectoderm, mesoderm, endoderm.
• Ectoderm is a germ layer developing into skin and nervous system.
• Mesoderm is a germ layer forming muscles, bones, and organs.
• Endoderm is a germ layer giving rise to digestive and respiratory systems.
• Invagination is when cells fold inward forming a pocket during gastrulation.
• Involution is when cells roll over an edge into the interior.
• Epiboly is when cells spread to enclose deeper layers.
• The fast block is the electrical barrier preventing additional sperm binding.
• The slow block is the cortical reaction creating a physical barrier post-fertilization.
• The blastocoel is the fluid-filled cavity within the blastula.
• Polyspermy prevention refers to mechanisms to block multiple sperm fertilizing an egg.
• The archenteron is a structure formed during gastrulation developing into digestive tube.
• Henen's node is the site of cell migration in bird gastrulation.
• The primitive streak is the area where cells migrate during gastrulation in birds and mammals.
• Superficial cleavage is when nuclei divide within common cytoplasm before cellularization.
• Radial cleavage is a type of cleavage with symmetrical cell division.
• Unequal cleavage is when cell sizes differ due to yolk distribution.
• The blastodisc is a disc-shaped structure formed on top of yolk in birds.
• Compaction is a process leading to inner cell mass formation in mammals.
• Cortical granules are enzymes modifying egg's outer layer during slow block.
• Extraembryonic membranes support and protect embryo without contributing to body structure.
• The amnion is a fluid-filled sac preventing desiccation around the embryo.
• The chorion is a membrane facilitating gas exchange for the embryo.
• The yolk sac is a nutritional source in egg-laying vertebrates.
• The allantois stores waste and contributes to mammalian placenta.

Temperature Regulation

• Ectotherms depend on external heat sources for regulation.
• Endotherms generate internal heat through metabolic processes.
• Poikilotherms' body temperature varies with environmental conditions.
• Homeotherms maintain constant body temperature despite external changes.
• Heterothermic organisms switch between ectothermic and endothermic states.
• Homeostasis is the regulation of the internal environment for stability.
• Feedback control involves sensors, control centers, and effectors.
• Negative feedback is a response that counteracts the stimulus to maintain balance.
• Positive feedback amplifies the stimulus for specific outcomes.
• Heat transfer mechanisms include conduction, convection, radiation, and evaporation.
• Thermoregulation is maintaining body temperature within specific boundaries.
• Ectotherm strategies involve behavioral adjustments for optimal heat regulation.
• Antifreeze proteins prevent ice formation in ectotherms during freezing temperatures.
• Endotherm strategies refer to methods used by endotherms to regulate body temperature.
• Daily regulation involves cooling and heating mechanisms for temperature maintenance.
• Hibernation is a low-energy state during winter for survival.
• Torpor is a short-term decreased activity to conserve energy.
• Fur/feathers adaptation involves shedding or growing for seasonal temperature changes.
• Endothermy costs includes their high energy demand requiring large food intake.
• Metabolic rates are high in endotherms increasing vulnerability to food scarcity.

Respiration

• Fick's Law of Diffusion; rate of gas exchange depends on area, pressure, thickness.
• Surface area in Gas Exchange: increased area enhances efficiency in gas exchange.
• Thin Respiratory Surfaces have minimized distance for faster gas diffusion.
• Concentration Gradients are maintained by ventilation and countercurrent exchange.
• Gills Function through water flow allowing O2 diffusion into blood.
• Gill advantages include large surface area and efficient gas exchange.
• Gill disadvantages: inefficient in air; can collapse and dry out.
• Tracheal Systems allow for direct oxygen delivery in small-bodied animals.
• Cutaneous Respiration is gas exchange through moist skin in amphibians.
• Frog Lungs are simple sac-like with low efficiency.
• Bird Lungs are rigid with air sacs for continuous flow.
• Mammal Lungs are highly branched, alveolar lungs for moderate efficiency.

Circulation

• Open Circulatory System: hemolymph pumped into open spaces in arthropods.
• Closed Circulatory System: blood confined to vessels for efficient transport.
• The multi-chambered heart is an evolutionary adaptation for efficient blood circulation.
• Fish Heart Structure: 2 chambers with simple circulation.
• Amphibian Heart Structure: 3 chambers with partial separation of blood.
• Birds and Mammals Heart Structure: 4 chambers for complete blood separation.
• Double Circulation: Separate circuits for pulmonary and systemic blood flow.
• Oxygen Delivery Efficiency: High efficiency necessary for warm-blooded animals.