Textbook Definitions - Chapters 3 Flashcards
What are resources?
All things consumed by an organism, including space for shelter, food, mates etc.
Explain how organisms compete for resources
A rabbit eaten by an eagle is no longer available to another eagle
Solar radiation is the only source of energy that can be used in metabolic activities by green plants. What are the three ways a plant intercepts radiant energy?
Energy may be reflected, transmitted, or absorbed by the plant.
Radiant energy that has been fixed in photosynthesis passes just once through the world. But what happens if the radiation is not captured by the leaf?
It is lost forever.
What is photosynthetically active radiation (PAR)?
designates the spectral range of solar radiation from 400 to 700 nanometers that photosynthetic organisms are able to use in the process of photosynthesis.
What is, and what is the consequence of photoinhibtion of photosynthesis?
Photoinhibition is such that the rate of fixation of carbon decreases with increasing radiation intensity. IN simple: Plants need radiation but too much can lead them to overheat, or reduce the carbon in the air leaving them “hungry”.
Explain systematic variations in solar radiation.
Annually, green plants experience periods of famine (under supply) and glut (oversupply). Deciduous trees lose their leaves in the fall because they do not need them.
What is a resource depletion zone (RDZ)?
– a moving band of shadow over other leaves of the same plant, or of others. Occurs less in the water as everything is constantly moving but still occurs due to phytoplankton and algae.
Sun vs. shade species (terrestrial) and their reaction to systematic variations in the intensity of radiation
In general, plant species that are characteristic of shaded habitats use radiation at low intensities more efficiently than sun species, but the reverse is true at high intensities.
Sun vs. shade leaves
Sun leaves (located in sunny areas):
Are typically smaller, thicker, have more cells per unit area, denser veins, more densely packed chloroplasts and a greater dry weight per unit area of leaf. Leaves are more angled.
Shade leaves (located in shady areas):
Shade leaves are larger and thinner than normal sun leaves, and often appear a darker green (they contain more chlorophyll on a weight basis). Leaves are more horizontal.
The leave that a plant forms is in response to its environmental conditions since it can not easily change the leaf once it is made. BUT it can change its rate of photosynthesis extremely rapidly.
Pigment variation in aquatic species
Of the three types of pigment – chlorophylls, carotenoids and biliproteins – all photosynthetic plants contain the first two, but many algae also contain biliproteins; and within the chlorophylls, all higher plants have chlorophyll a and b, but many algae have only chlorophyll a and some have chlorophyll a and c.
What is the compensation point?
is the intensity of PAR at which the gain from gross photosynthesis exactly balances the respiratory and other losses (as accounted for in net photosynthesis).
What is the difference between gross and net photosynthesis?
Gross - the rate at which a plant captures radiant energy and fixes it in organic carbon compounds
Net - is the increase (or decrease) in dry matter that results from the difference between gross photosynthesis and the losses due to respiration and the death of plant parts
Define photosynthetic capacity
This is the rate of photosynthesis when incident radiation is saturating, temperature is optimal, relative humidity is high, and CO2 and oxygen concentrations are normal.
Ex. Species from resource-poor (limited water and nutrients) environments (e.g. shade plants, desert perennials) usually have low photosynthetic capacity.
What are some things that limit the rate of photosynthesis?
- Leaf nitrogen content
- Environmental conditions (e.g. temperature)
- Availability of resources other than radiant energy
- How often the plant is plucked
Explain the stomatal opening
Prime route of CO2 entry, but as they are open water will also evaporate out them.
What goes into determining how efficiently a plant absorbs CO2 and at the same time reduces its water loss (in reference to the stomata)
- short active interludes in a dormant life
- leaf appearance and structure
- physiological strategies
pg. 68
Explain the three different ways plants carry out photosynthesis: C3, C4 and CAM
C3 - 85% of plants use this type. CO2 is fixed into a three-carbon acid by the enzyme Rubisco, which is present in massive amounts in the leaves. Most energy efficient method (they do better in high atmospheric concentrations of CO2 than C4 plants). But loses water through photorespiration.
C4 - the C3 pathway is present but it is confined to cells deep in the body of the leaf. CO2 that diffuses into the leaves via the stomata meets mesophyll cells containing the enzyme phosphoenolpyruvate (PEP) carboxylase. This enzyme combines atmospheric CO2 with PEP to produce a four-carbon acid. This diffuses, and releases CO2 to the inner cells where it enters the traditional C3 pathway. Can absorb atmospheric CO2 much more effectively than C3 plants. As a result, C4 plants may lose much less water per unit of carbon fixed. But C4 system has a high light compensation point and is inefficient at low light intensities; C4 species are therefore ineffective as shade plants.
CAM - Same process as C4 but is carried out durin gthe night. Organisms absorb sunlight energy during the day then use the energy to fix carbon dioxide molecules during the night. During the day, the organism’s stomata close up to resist dehydration while the carbon dioxide from the previous night undergoes the Calvin cycle. CAM photosynthesis allows plants to survive in arid climates and therefore is the type of photosynthesis used by cacti and other desert plants.
Consequences of rising CO2 levels on photosynthesis?
- change the composition of plants, and in particular to reduce nitrogen concentration in above-ground plant tissues
- CO2 enhancement may also reduce concentrations in plants of other essential nutrients and micronutrient
Define field capacity
The water held by soil pores against the force of gravity
Define permanent wilting point
The minimum amount of water in the soil that the plant requires not to wilt.
Explain resource depletion zone (RDZ) of plant roots
As a root withdraws water from the soil pores at its surface, it creates water-depletion zones around it. These determine gradients of water potential between the interconnected soil pores. Water flows along the gradient into the depleted zones, supplying further water to the root. RDZ’s also occur for minerals.
Autotrophs versus heterotrophs
Autotroph - green plants and certain bacteria. Turn inorganic compounds into organic compounds to use as energy. Resources for heterotrophs.
Heterotroph - decomposers, predators, grazers, and parasites.
Define: Saprotrophs Predators Grazers Parasites
Saprotrophs - bacteria, fungi and detritivorous animals -use other organisms, or parts of other organisms, as food but only after they have died.
Predators - use other living organisms, or parts of other living organisms, as food.
Grazers - regarded as a type of predation, but the food (prey) organism is not killed; only part of the prey is taken, leaving the remainder with the potential to regenerate.
Parasites - a form of predation in which the consumer usually does not kill its food organism; but unlike a grazer, a parasite feeds from only one or a very few host organisms in its lifetime
