Plant Evolution Flashcards
What is the structure of byrophytes?
Never have roots, contain rhizoids, simple leaves and stems are non-vascular
What is the structure of filicinophytes?
Vascular roots, leaves & non-woody stems
What is the structure of conferophytes?
Trees or shrubs with woody vascular tissues, narrow leaves with thick waxy cuticle
What is the structure of angiospermophytes?
Roots, leaves and stems, vascular tissue, some stems are herbaceous others woody
What adaptations of vascular plants has helped their success on land?
Regional specialization of body; roots stems and leave. Structural support to stand on land. Vascular system. Pollen, eliminated need for water to transport gametes, seeds, and dominance of sporophyte
Draw and label the distribution of tissues in the stem
Refer to image
Explain the relationship between the distribution of tissues in the leaf and the functions of these tissues
Epidermis on the outside: Stomata on underside of leaf; allows exchange of gases
Ground tissue: palisade parenchyma = site of most photosynthesis. Spongy parenchyma =
gases circulate.
Vascular tissue: branches into leaf traces for support and improved transport of water/nutrients
What are three characteristics of monocotyledonous plants?
embryos have one cotyledon, leaf has veins that are usually parallel, stems are vascular bundles usually complexly arranged
What are three characteristics of dicotyledonous plants?
embryos have two cotyledons, leaves have veins that are usually netlike, and stems are vascular bundles usually arranged in a ring
What is the function of apical meristems in dicots?
Allow plant to grow in length and serves as the primary growth
What is the function of lateral meristems in dicots?
Allows the plant to grow in girth (stems in woody plants) serves as the secondary growth
Explain the role of auxin in phototropism as an example of the control of plant growth
Auxin is responsible for promoting elongation on the shaded side of a plant stem. This allows the stem to grow towards the light source. The hormone accumulates on the shaded side, causing cells on that side to grow longer and thus bending the stem towards the light.
What is a storage organ?
A storage organ is a part of a plant specifically modified to store energy (e.g. carbohydrates) or water
Where are the storage organs in plants found?
They are usually found underground (better protection from herbivores) and may result from modifications to roots, stems or leaves:
What is a storage root?
Modified roots that store water or food (e.g. carrots)
What are stem tubers?
Horizontal underground stems that store carbohydrates (e.g. potato)
What are bulbs?
Modified leaf bases (may be found as underground vertical shoots) that contain layers called scales (e.g. onion)
How do succulents enable water storage?
modified leaves or stems (thickened, fleshy and wax-covered) to enable water storage
How do other plants modify to support climbing and attachment? What is this modification called?
Other plants (e.g. vines) have modifications to their leaf or stem to enable climbing support and attachment - these are called tendrils
Outline four adaptations of xerophytes
small or compound leaves, deep root systems, spines, waxy cuticle development, and a variety of stomata adaptations.
State the significance of thickened cellulose in terrestrial plants
Thickening of the cell wall provides extra structural support
State the significance of cell turgor in terrestrial plants
Increased hydrostatic pressure within the cell exerts pressure on the cell wall, making cells turgid
State the significance of lignified xylem in terrestrial plants
Xylem vessels run the length of the stem and branches, lignification of these vessels provides extra support
Explain how the root system provides a large surface area for mineral ion and water uptake
Plants take in water and essential minerals through their roots; thus need a large surface area in order to optimize the uptake. The ‘extensive’ branching of the roots and the growth of root hairs allows for the plant to increase its mineral ion absorption and surface area of water.
List three ways in which mineral ions in the soil move to the root
Diffusion, mass flow, and fungal hyphae
What is diffusion?
Movement of minerals along a concentration gradient
What is mass flow?
Uptake of mineral ions by means of a hydrostatic pressure gradient
What is Fungal Hyphae
Absorb minerals from the soil and exchange with sugars from the plant (mutualism)
Define transpiration
Transpiration is loss of water from the stomata of leaves
Explain how guard cells regulate transpiration
Stomata consist of microscopic pores, each flanked by a pair of guard cells. Guard cells can increase or decrease the size of the pore via changes in their turgor status, hence regulating both CO2 entry into the leaf and transpiration, or the loss of water from the leaf.
State the function of abscisic acid in regulating the stomata
A typical effect of ABA on leaves is to reduce transpirational water loss by closing stomata and parallelly defend against microbes by restricting their entry through stomatal pores.
Explain how abiotic factors (light temperature wind and humidity) affect the rate of transpiration
High temperatures increase evaporation rate of water.
High humidity lowers the rate of water evaporation.
High light intensity usually increases photosynthesis which increases transpiration.
Outline the role of phloem in active translocation of sugars and amino acids from source to sink
Phloem tissue transports sugars and amino acids from sources which include photosynthetic tissue (leaves and stems) and storage organs, to sinks which include the fruits, seeds and roots of the plant.
This transport is known as active translocation and requires energy.
Draw and label the structure of a dicotyledonous animal-pollinated flower
refer to image
Define pollination
the placement of pollen on the stigma. The transfer of pollen grains from the anther to the stigma (usually of another plant), often facilitated by animals, wind or water movement
Define fertilization
a process of sexual reproduction, which occurs after pollination and germination. Fusion of the male gamete nuclei (in the pollen grain) with the female gamete (in the ovule) to form a zygote
Define seed dispersal
Fertilized ovules form seeds that move away from the parental plant before germination, reducing competition for resources
Draw and label a diagram of the internal and external structure of a named dicotyledonous seed
refer to image
Describe the metabolic events of germination in a typical starchy seed
The absorption of water followed by the formation of gibberellin in the emery cotyledon, This stimulates the production of amylase which catalyzes the breakdown of starch into maltose. This maltose then diffuses to the embryo for energy release and growth
Explain the conditions needed for the germination of a typical seed
Germination is the emergence and growth of an embryonic plant from a seed. Water is needed to metabolically activate the cells, proper temperature for optimal functions of enzymes, and oxygen for aerobic respiration (need ATP in order to grow).
What happens if the conditions for germination of a typical seed are not favorable?
If conditions are not favorable then the seed may remain dormant. This way the seed can survive adverse conditions and only start to germinate when conditions become favorable.
Explain how flowering is controlled in long-day and short-day plants
Flowering in long-day and short-day plants is controlled by a pigment called phytochrome. This pigment exists in two forms, P(sub)r and P(sub)fr which can be converted into each other.
What is P(sub)fr and P(sub)r?
The Pfr form is the active form of phytochrome, while the Pr form is the inactive form of phytochrome
When does P(sub)fr and P(sub)r, convert into each other?
Sunlight contains more red light, so the Pfr form is predominant during the day, with the gradual reversion to the Pr form occurring at night
When is flowering induced in long day plants?
In long day plants, the active Pr form is a promoter of flowering and so flowering is induced when the night period is less than a critical length and Pfr levels are high
When is flowering induced in short day plants?
In short day plants, the active Pfr form is an inhibitor of flowering and so flowering is induced when the night period is greater than a critical length and Pfr levels are low
How does the structure of xylem vessels aid the transpiration stream?
The outer cell walls contain thickenings which resemble spirals/rings with lignin which makes the vessels strong and able to withstand low pressures.
How does evaporation aid the transpiration stream?
Due to evaporation of water from the leaf, the transpiration pull occurs (more water to be pulled up xylem tube due to low pressure)
How does cohesion/adhesion aid the transpiration stream?
Columns of water do not break due to cohesion and adhesion of water molecules (cohesion of water molecules and adhesion of water molecules to walls of xylem)
What is transpiration pull?
low pressure causes more water from the roots to be pulled upwards through the xylem tubes, this is called transpiration pull.
