Plants Evolution Flashcards
Outline the wide diversity in the plant kingdom as exemplified by the structural differences between bryophytes, filicinophytes, coniferophytes, and angiospermophytes
-Bryophytes: Never have roots, contain rhizoids, simple leaves, and stems are non-vascular
-Filicinophyte: Vascular roots, leaves & non-woody stems
-Coniferophytes: Trees or shrubs with woody vascular tissues, narrow leaves with a thick waxy cuticle
-Angiospermophytes: Roots, leaves and stems, vascular tissue, some stems are herbaceous others woody
Describe adaptations of vascular plants that have contributed to their success on land
Regional specialization of the body (roots stems and leave). Structural support to stand on land. Vascular system. Pollen: eliminating the need for water to transport gametes, seeds, and the dominance of sporophytes.
Explain the relationship between the distribution of tissues in the leaf and the functions of these tissues
Epidermis on the outside: Stomata on the underside of the leaf; allows the 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
Explain three differences between monocotyledonous and dicotyledonous plants
Monocots: embryos have one cotyledon, the leaf has veins that are usually parallel, stems are vascular bundles usually complexly arranged
Dicots: embryos have two cotyledons, leaves have veins that are usually netlike, and stems are vascular bundles usually arranged in a ring
Discuss the function of apical and lateral meristems in dicots
Apical: Allows the plant to grow in length and serves as the primary growth
Lateral: Allows the plant to grow in girth (stems in woody plants) and 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.
Identify modifications of roots, stems, and leaves for different functions bulbs, stem tubers, storage roots, and tendrils
A storage organ is part of a plant specifically modified to store energy (e.g. carbohydrates) or water
They are usually found underground (better protection from herbivores) and may result from modifications to roots, stems or leaves:
Storage roots: Modified roots that store water or food (e.g. carrots)
Stem tubers: Horizontal underground stems that store carbohydrates (e.g. potato)
Bulbs: Modified leaf bases (may be found as underground vertical shoots) that contain layers called scales (e.g. onion)
Some plants (called succulents) have modified leaves or stems (thickened, fleshy and wax-covered) to enable water storage (e.g. cacti)
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
- A variety of stomata adaptations.
State the significance of thickened cellulose, cell turgor, and lignified xylem in terrestrial plants
Three ways by which terrestrial plants may support themselves are:
Thickened cellulose: Thickening of the cell wall provides extra structural support
Cell turgor: Increased hydrostatic pressure within the cell exerts pressure on the cell wall, making cells turgid
Lignified xylem: 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: Movement of minerals along a concentration gradient
Mass Flow: Uptake of mineral ions by means of a hydrostatic pressure gradient; water is taken into roots via osmosis, creating a negative hydrostatic pressure in the soil. Minerals form hydrogen bonds with water molecules and are dragged to the root, concentrating them for absorption
Fungal Hyphae: Absorb minerals from the soil and exchange them with sugars from the plant (mutualism)
Define transpiration
Transpiration is the loss of water from the stomata of leaves
Explain how water is carried by the transpiration stream (include the structure of xylem vessels, transpiration pull, cohesion, adhesion, and evaporation)
Transportation creates negative pressures and forces fluid up the xylem, it is assisted by cohesion and adhesion
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 the 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 the 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.
Distinguish between pollination fertilization and seed dispersal
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
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
Seed dispersal: Fertilised ovules form seeds that move away from the parental plant before germination, reducing competition for resources
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).
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).
Explain how flowering is controlled in long-day and short-day plants, including the role of phytochrome
Flowering in long-day and short-day plants is controlled by a pigment called phytochrome. This pigment exists in two forms, Pr and Pfr which can be converted into each other.
The Pfr form is the active form of phytochrome, while the Pr form is the inactive form of phytochrome
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
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
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
