IB HL BIO YR 2 UNIT FOUR

cohesion

attraction between the same kind of molecules, hydrogen bonds, enables surface tension and water transport in plants, ensures a continuous column of water in the xylem, ex- water binding to water

adhesion

attraction between different kinds of molecules, hydrogen bonds, responsible for water transport in plants/capillary action, directly causes water molecules to stick to the xylem wall, cell adhesion/multicellularity, blood movement, ex- water binding to a different polar molecule

covalent bonding

bonds formed when electrons are shared, forms DNA (holds nucleotides together) and proteins (links amino acids), ex- water and carbon dioxide

universal solvent

water is called this because it allows a wide variety of hydrophilic substances to dissolve in it because of its polarity and because it is the medium for all metabolic reactions

water

polar covalent molecule, oxygen has a partial negative charge and hydrogens have partial positive charges, electrons are unevenly shared, universal solvent, forms hydrogen bonds with other ___ molecules

surface tension

the property of a substance to resist an external force, water has a strong one because of the cohesive nature of water molecules, helps create habitats for animals like the water strider

xylem vessels

thin narrow tubes which transport water (and dissolved minerals) from the roots to the leaves of plants, cohesion/adhesion/tension of water allows it to form a continuous column up plants, water in this is under tension because of evaporation, contain pits in their walls for lateral movement of water between vessels

capillary action

the ability of water to flow against gravity in a narrow space, greater in fine clay soils, and weaker in porous sandy soils, water moving up towards roots

apoplast pathway

allows water and dissolved nutrients to move through the cell walls of plants, polar water adheres to polar cellulose

Hydrophilic substances

charged substances that mix and dissolve with water

pollination

transfer of pollen from male anther to female stigma

fertilization

sperm in pollen tube fuses with egg in an ovule, happen in the ovary of the carpel, produces zygote

seed dispersal

movement of seed away from parent plant

petal (animal pollinated flower)

colorful, large, and scented to attract pollinators

petal (wind pollinated flower)

smaller because no need to attract pollinators, can still be colorful and/or scented but doesn’t really matter

stamen (animal pollinated flower)

male part of the plant, made up of anther and filament, short, inside the plant

stamen (wind pollinated flower)

male part of the plant, made up of anther and filament, long filaments, outside the plant

stigma (animal pollinated flower)

sticky tip of the carpel, traps pollen, inside flower so it can brush against animals that enter flower

stigma (wind pollinated flower)

sticky tip of the carpel, traps pollen, hangs outside flower to trap pollen that blows past it

pollen (animal pollinated flower)

makes lower quantities of sticky pollen, attaches to bodies of animal pollinators

pollen (wind pollinated flower)

large quantities of light, feathery pollen that is easily carried by the wind

style

connects the stigma and the ovary, pollen tube grows down it, part of the carpel

ovary

contains ovules with haploid eggs, bottom part of the carpel, where fertilization occurs, swollen base of the pistil that contains the ovules and develops into the fruit after fertilization

carpel

female part of the plant, contains stigma, style, and ovary

anther

produces pollen grains that contain haploid sperm, part of stamen

filament

supports another, brings anther into contact with animal pollinator or wind, part of stamen

sepal

protects flower before it blooms

steps to fertilization in flowering plants

pollen produces pollen tube after landing on stigma, tube grows down style into ovary, 2 sperm travel down tube, pollen tube enters ovule, one sperm fuses with egg cell, forms zygote that undergoes mitosis and cytokinesis to make an embryo, second sperm cell fuses with 2 polar nuclei to form triploid endosperm that provides nutrients for developing embryo

triploid endosperm

fusion of second sperm cell and two polar nuclei, provides nutrients for developing embryo

self pollination

reduces genetic diversity within a population, sperm and egg come from same flower

cross pollination

plant reproduction with two different parents, increases genetic diversity

factors that reduce chance of self pollination

different maturation times for pollen and style, same plant but different male and female flowers, same species but different male and female plants

germination

development and growth of the plant embryo into a seedling, ends when shoot emerges from seed

germination steps

1. water is absorbed into the seed

2. gibberellin is made

3. gibberellin stimulates synthesis of digestive enzymes (amylase)

4. amylase digests stored starch to turn it into maltose

5. maltase further digests the maltose into glucose

6. embryonic plant cells use oxygen and glucose for aerobic respiration

7. respiring embryo grows using nutrients stored in the seed

phytohormones

plant hormones that regulate growth and development in plants

tropism

growth in response to a stimulus

positive phototropism

growth of a plant part towards light

auxin

causes elongation of cells in shoots by activating specific genes, can diffuse into plant cells but not out of, produced by shoot tips and transported to roots

auxin efflux carriers

protein pumps that actively transports auxin out of a plant cell, auxin moves from the light side to the shaded side, increased auxin concentration builds up on the shaded side and causes it to bend towards light

cytokinin

plant hormones, promote cell growth and differentiation, produced by root tops and transported to shoots

ethylene

promotes fruit ripening, receptors on the fruits’ surface detect this and it stimulates a positive feedback loop where the fruit produces more of it to stimulate various enzymes involved in fruit ripening

waxy cuticle

reduces water evaporation in leaves, clear to let sunlight pass

epidermis

protects mesophyll cells, clear to let sunlight pass, higher stomatal density on the lower one than the upper one (has almost no stomata)

spongy mesophyll

increases surface area for gas exchange, surrounded by air spaces

air spaces

facilitate gas exchange between atmosphere and mesophyll

stomata

pores on the bottom of leaves, allow gasses to enter and exit leaf, opened and closed by guard cells

veins

support leaf, made of xylem and phloem

monocot

one cotyledon (leaf) in its seed, fibrous/branched/shallow roots, scattered vascular system, parallel veins on leaves, flowers have petals in multiples of three

dicot

two cotyledons (leafs) in its seed, tap roots, thick roots with fibers that are deeper and more secure, ringed vascular system, branched veins on leaves, flowers have petals in multiples of 4-5

transpiration

movement of water through a plant and its evaporation from aerial parts of the plant/leaves, inevitable consequence of gas exchange (as o2 and co2 enter/exit leaves, water is bound to leave, too), water evaporates from mesophyll cells and then diffuses through stomata

factors impacting rate of transpiration

1. light intensity increases, more stomata opens, more oxygen diffused out, increased RoT

2. temperature increases, water particles gain kinetic energy, move faster, diffuse out of leaf at a faster rate, also evaporates more because its hotter, increased RoT

3. air flow/wind increases, wind moves water vapor away from the leaf, decreases the concentration of water around the leaf to increase concentration gradient, increased RoT

4. humidity increases, concentration around leaf increases, decreases water concentration gradient, slower diffusion, decreased RoT

stomatal density

number of stomata per unit of area of a leaf, = (avg # of stomata counted) / (area of microscope FOV (mm²))

xylem

thick walls for structural support, transport water and dissolved minerals up a plant, dead ____ cells make up ____ vessels, negative pressure potential draws water up this, no end walls between cells to allow water to move up a plant, no cell contents/plasma membrane

phloem

transports nutrients (amino acids, glucose, etc) down and sometimes up the plant

sieve tubes

sieve elements form long and narrow tubes, reduced cytoplasm and no nucleus to allow movement of cell swap, plasma membranes with co-transporter protein pumps for active transport to move protons in→creates proton gradient→sucrose moves into tube, have sieve plates and plasmodesmata

sieve plates

pores that allow cell sap with nutrients to flow from cell to cell in the sieve tube

plasmodesmata

allows direct connections between sieve cytoplasm and companion cell cytoplasm

lignin

strengthens cell walls of xylem, resists inward pressure made by transportation, structural support, made of proteins

companion cells

provide metabolic support for sieve tube cells, cytoplasm is directly connected to sieve cytoplasm through plasmodesmata, large number of mitochondria to pump ATP into sieve cells via transport proteins and protein pumps

translocation

movement of nutrients (aas and sucrose) up or down the stem of a plant through the phloem, moves nutrients from a source (where theyre produced/stored) to a sink (where theyre used/stored)

translocation steps

1. sucrose is produced by leaves through photosynthesis

2. sucrose is actively transported by companion cells into sieve tubes against the concentration gradient (phloem loading, creates a high sucrose concentration in the phloem sieve tubes)

3. water moves into the phloem from the xylem by osmosis because xylem is hypotonic and phloem is hypertonic

4. hydrostatic pressure builds up in the sieve tubes in the leaves because water is incompressible

water potential

potential energy of water per unit of volume, used to quantify the tendency of water to osmosis, measured in kPa, represented by the ψ_W symbol, equals solute potential plus pressure potential

solute potential

becomes more negative as solute concentration increases, equals zero at pure water, cannot be positive

pressure potential

equals zero at atmospheric pressure, increases when pressure increases and vice versa, can be positive (like when hydrostatic pressure increases or solute concentration decreases) or negative (like when hydrostatic pressure decreases-transpiration or solute concentration increases)

When plant tissue cells are in a hypertonic solution

water moves out of the cell, ψP decreases because less pressure, cell membrane pulls away from cell wall (flaccid), ψS increases because the solute concentration increases (because there's less water), overall water potential decreases

When plant tissue cells are in a hypotonic solution

water moves into the cell, ψP increases, increased pressure causes membrane to exert more pressure on the cell wall (turgid), ψS decreases because solute concentration decreases (because there's more water), overall water potential increases

apical dominance

the main, central stem (the "apex") grows taller and stronger than side branches, inhibiting their growth, controlled by auxin

root pressure

the hydrostatic pressure exerted by the roots of a plant, drives water and nutrient uptake from the soil and into the plant's vascular tissue (xylem)

Potometer

an apparatus used to measure the rate of water uptake by a plant shoot, measures rate of transpiration

Palisade mesophyll

layer of tightly packed, elongated cells, beneath the upper epidermis of leaves, containing numerous chloroplasts, primary site for photosynthesis in most plants

pollen

produced in the anther and contain the male gametes (sperm cells)

embryo

The part of the seed that grows into a new plant

radicle

the embryonic root that emerges first during seed germination and develops into the primary root system of the plant

gibberellin

helps break seed dormancy by promoting germination

cotyledon

seed leaves that serve as a food storage organ for nutrients needed during early seedling growth, first leaf that photosynthesizes

peduncle

stalk or stem that supports and connects the flower to the main stem or branch of the plant, flower's support system that delivers water and nutrients

receptacle

the enlarged end of the flower stalk that serves as the base on which all other floral parts are attached, foundation for all parts of the flower

xerophytic plants

type of plant that has adaptations to survive in an environment with little liquid water, have stomata sunken in pits to reduce water loss through transpiration by creating small pockets of humid air around the stomata

phytochrome

photoreceptor proteins in plants that detect light levels, influencing various developmental processes like seed germination, flowering, and seedling growth