Studied by 9 people
Origin of land plants
All green algae and land plants share a common ancestor over 1 billion years ago, supported by DNA sequence data.
Challenges on land
Plants had to overcome issues like water loss, sun protection, and effective gamete dissemination.
Adaptations to terrestrial life
Plants evolved mechanisms like moving water within, specialized vascular tissues (xylem and phloem), and waxy cuticles for protection.
Haplodiplontic life cycle
All land plants exhibit a life cycle with multicellular haploid and diploid stages, known as alternation of generations.
Bryophytes
Mosses, the closest living descendants of early land plants, lack tracheids but have conducting cells and mycorrhizal associations.
Vascular plants
Have xylem and phloem for water and nutrient transport, enabling height growth and hormone distribution.
Plant cell types
Dermal tissue protects, ground tissue supports and stores, and vascular tissue conducts water and nutrients.
Meristem cell division
Meristems at tips and roots produce new cells, while lateral meristems increase stem/root diameter.
Roots
Anchor plants and absorb water; consist of root cap, cell division, elongation, and maturation zones.
Stems
Support above-ground organs, grow from apical and lateral meristems, and have vascular tissue organization differences in monocots and eudicots.
Leaves
Photosynthetic organs with different morphological groups like microphylls and megaphylls, and eudicot leaves with flattened blades and petioles.
Transport in Plants
Water and minerals enter roots, move through xylem, and exit through stomata due to cohesion, adhesion, and osmosis.
Osmotic concentration
Refers to the concentration of solutes in a solution.
Hypertonic
Describes a solution with a higher solute concentration compared to another solution.
Hypotonic
Describes a solution with a lower solute concentration compared to another solution.
Isotonic
Refers to two solutions having the same concentration of solutes.
Osmosis
The movement of water across a semipermeable membrane from an area of low solute concentration to an area of high solute concentration.
Turgid
The swollen state of a plant cell due to high water uptake.
Plasmolysis
The shrinking of a cell due to water loss.
Osmotic pressure
The force required to prevent the flow of water across a semipermeable membrane.
Water potential
The energy status of water in a system, influenced by solute concentration and pressure.
Xylem transport
The movement of water and minerals through the xylem tissue in plants.
Guard cells
Specialized cells that control the opening and closing of stomata.
Stomatal opening
The process by which stomata open due to turgor pressure in guard cells.
Phloem transport
The movement of carbohydrates and other substances through the phloem tissue in plants.
Pressure flow hypothesis
A model explaining the movement of carbohydrates in the phloem from source to sink tissues.
Topsoil
The upper layer of soil where most plant roots are found, containing a mixture of mineral particles, organisms, and humus.
Suberin
Found in cell walls of subterranean plant organs
Physical damage and pathogens
Damage to dermal surface can create entry site for pathogens
Fungal invasion phases
Windblown spore lands, germinates, forms adhesion pad, hyphae grow, differentiate into haustoria
Chemical defenses
Plants employ toxins to kill herbivores or deter grazing behavior
Secondary metabolites
Modified pathways produce chemicals affecting herbivores like alkaloids, tannins, and plant oils
Allelopathic plants
Secrete chemicals to inhibit growth of nearby plants, reducing competition
Ricin poison
Alkaloid from castor bean plant, can be lethal, blocks protein translation
Plant protection by animals
Ants protect acacia trees from harmful herbivores
Plant sensory systems
Response to light, gravity, and hormones like auxin
Photomorphogenesis
Phytochrome involved in light-triggered development, seed germination, and shoot elongation
Phototropism
Directional growth response to light, compensating for plant immobility
Blue light receptors
Phototropin 1 regulates auxin flux in shoots in response to blue light
Gravitropism
Plant response to gravity, shoots exhibit negative gravitropism, roots positive
Amyloplasts
Starch-storing organelles involved in gravity perception in roots
Hormones and sensory systems
Auxin promotes cell growth and influences plant bending towards light
Flowering pathways
Light, temperature, gibberellin, and autonomous pathways regulate flowering in plants
Flower morphology
Calyx, corolla, androecium, and gynoecium make up the structure of flowers
Embryo development
Double fertilization, embryo differentiation, and formation of tissue systems in plants
Germination
Emergence of radicle through seed coat, requires water, oxygen, and metabolic reserves
Patterns of Behavior
Once initiated, behaviors tend to continue to completion even if the initial stimulus is removed.
Neural Mechanisms
Rapid behaviors are controlled by simple neural mechanisms involving a few neurons.
Hormonal Influence
Hormones like testosterone, estrogen, and glucocorticoids influence behaviors such as territorial behavior, courtship, mating, and stress.
Neurotransmitters
Chemicals like serotonin and dopamine influence behaviors.
fMRI
Functional Magnetic Resonance Imaging is used to measure neuron activity.
Behavioral Genetics
Study of how genetics and environmental factors influence behavior.
Vasopressin and Oxytocin
Hormones released during mating that regulate water retention and birth contractions.
Habituation
Decrease in response to repeated stimuli without positive or negative consequences.
Associative Learning
Conditioning where behaviors are learned through associations between stimuli or responses.
Operant Conditioning
Learning through trial and error by associating behaviors with rewards or punishments.
Instincts
Innate behaviors that guide learning and associations.
Imprinting
Forming social attachments or preferences that influence behavior later in life.
Evolutionary Factors
Selection, mutation, and genetic variation influence changes in populations and species.
Species Concepts
Biological species concept defines species as reproductively isolated groups.
Speciation
Allopatric speciation results from geographic isolation, leading to the formation of new species.
Adaptive Radiation
Occurs in new environments with abundant resources and few species, leading to diversification.
Taxonomy
Science of classifying organisms into groups based on shared characteristics.
Monophyletic Group
Group of organisms including a common ancestor and all its descendants.
Root system
anchors the plant and used to absorb water and ions from the soil
shoot system
consists of supporting stems, photosynthetic leaves, and reproductive flowers. Repetitive units consist of internode, node, leaf and axillary bud.
meristems
· Located at the tips of stems and roots
· Produce hormones that repress the development of the lateral bud
· When meristem is interrupted, the plant will no longer be able to grow from that tip.
· Lateral buds will then be released from the repression
types of plant tissue
dermal, ground, and vascular
dermal plant tissue
· Forms the epidermis
· One cell layer thick
· Forms the outer protective covering of the plant
· Covered with fatty cutin layer
· Mostly epidermal cells
· Also consists of special cells, including guard cells, trichomes, and root hairs.
ground plant tissue types
Parenchyma, Collenchyma, Sclerenchyma
parenchyma
function in storage, photosynthesis and secretion
· Most common type of plant cell
· Living protoplasts
· Most only have primary cell walls
collenchyma
protection and support
· Provides flexible support for plant organs
· Allows bending without breaking
· Living protoplasts
· Lacks secondary cell walls
sclerenchyma
protection and support
· Tough thick walls
· Usually lack living protoplasts at maturity
· Secondary cell walls often contain lignin
· Two general types, fibers and sclereids. Both strengthen tissues.
all plants are…
haplodiplontic
Note 
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