Textbook Definitions - Chapters 3

Question 1

What are resources?

Answer 1

All things consumed by an organism, including space for shelter, food, mates etc.

Question 2

Explain how organisms compete for resources

Answer 2

A rabbit eaten by an eagle is no longer available to another eagle

Question 3

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?

Answer 3

Energy may be reflected, transmitted, or absorbed by the plant.

Question 4

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?

Answer 4

It is lost forever.

Question 5

What is photosynthetically active radiation (PAR)?

Answer 5

designates the spectral range of solar radiation from 400 to 700 nanometers that photosynthetic organisms are able to use in the process of photosynthesis.

Question 6

What is, and what is the consequence of photoinhibtion of photosynthesis?

Answer 6

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”.

Question 7

Explain systematic variations in solar radiation.

Answer 7

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.

Question 8

What is a resource depletion zone (RDZ)?

Answer 8

– 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.

Question 9

Sun vs. shade species (terrestrial) and their reaction to systematic variations in the intensity of radiation

Answer 9

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.

Question 10

Sun vs. shade leaves

Answer 10

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.

Question 11

Pigment variation in aquatic species

Answer 11

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.

Question 12

What is the compensation point?

Answer 12

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).

Question 13

What is the difference between gross and net photosynthesis?

Answer 13

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

Question 14

Define photosynthetic capacity

Answer 14

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.

Question 15

What are some things that limit the rate of photosynthesis?

Answer 15

• Leaf nitrogen content
• Environmental conditions (e.g. temperature)
• Availability of resources other than radiant energy
• How often the plant is plucked

Question 16

Explain the stomatal opening

Answer 16

Prime route of CO2 entry, but as they are open water will also evaporate out them.

Question 17

What goes into determining how efficiently a plant absorbs CO2 and at the same time reduces its water loss (in reference to the stomata)

Answer 17

• short active interludes in a dormant life
• leaf appearance and structure
• physiological strategies
  pg. 68

Question 18

Explain the three different ways plants carry out photosynthesis: C3, C4 and CAM

Answer 18

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.

Question 19

Consequences of rising CO2 levels on photosynthesis?

Answer 19

• 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

Question 20

Define field capacity

Answer 20

The water held by soil pores against the force of gravity

Question 21

Define permanent wilting point

Answer 21

The minimum amount of water in the soil that the plant requires not to wilt.

Question 22

Explain resource depletion zone (RDZ) of plant roots

Answer 22

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.

Question 23

Autotrophs versus heterotrophs

Answer 23

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.

Question 24

Define:
Saprotrophs
Predators
Grazers
Parasites

Answer 24

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

Question 25

Specialists versus generalists diets

Answer 25

Specialists - may consume only particular parts of their prey though they range over a number of species. Usually have shorter life spans.
Generalists - take a wide variety of prey species, though they very often have clear preferences and a rank order of what they will choose when there are alternatives available. Species with this diet usually have a long life span.

Question 26

Do plants or animals have a higher C:N (carbon:nitrogen) ratio?

Answer 26

Plants have a 40:1, animals, fungi, and bacteria only have a 10:1 ratio.
The presence of a cell wall in plant cells is largely responsible for the high fixed carbon content of plant tissues and the high ratio of carbon to other important elements. (Plants contain more fiber whereas, animals contain more fats and protein).

Question 27

Physical defense: Define coevolution

Answer 27

is the process by which two or more species evolve in tandem by exerting selection pressures on each other. Examples of coevolutionary systems include host and parasites, predators and prey, and mutualistic or symbiotic interactions.

Question 28

Physical defense: Importance of spines

Answer 28

Ex, The spiny leaves of holly are not eaten by oak eggar moth larvae, but if the spines are removed the leaves are eaten readily.

Question 29

Physical defense: Shells

Answer 29

the thick shell of a nut or the fibrous cone on a pine – is a defense if, as a consequence, the consumer eats less of it.

Question 30

Physical defense: Seeds

Answer 30

Some are dissipated, some are clumped together, some are protected by a spine or thick coating

Question 31

Chemical defenses: Apparency theory

Answer 31

This is based on the observation that noxious plant chemicals can be classified broadly into two types: (i) toxic (or qualitative) chemicals, which are poisonous even in small quantities; and (ii) digestion-reducing (or quantitative) chemicals, which act in proportion to their concentration. The theory further supposes that toxic chemicals, by virtue of their specificity, are likely to be the foundation of an arms race (coevolution), requiring an equally simple and specific response from a herbivore; whereas chemicals that make plants generally indigestible are much more difficult to overcome.

Question 32

Chemical defenses: Optimal defense theory

Answer 32

predicts that the more important an organ or tissue is for an organism’s fitness, the better protected it will be; and in the present context, it predicts that more important plant parts should be protected by constitutive chemicals (produced all the time), whereas less important parts should rely on inducible chemicals, only produced in response to damage itself.

Question 33

Define crypsis

Answer 33

An animal that matches its background, possesses a pattern that disrupts its outline, or resembles an inedible feature of its environment to avoid being preyed on. Ex, a grasshopper is green.

Question 34

Define aposematism

Answer 34

An animal that advertises their poison or toxin by being brightly coloured. Ex, black and yellow of wasps. Neon colours of some frogs.

Question 35

Define Batesian and Mullerian mimicry

Answer 35

Batesian mimicry is a form of mimicry where a harmless species has evolved to imitate the warning signals of a harmful species directed at a predator of them both. … It is often contrasted with Müllerian mimicry, a form of mutually beneficial convergence between two or more harmful species.

Question 36

Explain isoclines

Answer 36

Taking resources in pairs, plots (one species on the x-axis, the other on the y-axis) for the consumers of zero net growth isoclines allow resource pairs to be classified as:
Essential
Perfectly substitutable
Complementary
Antagonistic
Inhibition
The zero net growth isoclines themselves define a boundary of a species’ ecological niche.