Lecture 3 - DA Flashcards
What are 8 factors affecting community structure?
Light Temperature Water Wind Nutrients Slope/aspect Biotic Fire
What is a community structure determined by?
The environment and species interactions.
What always happens to growth rates? Name 3 reasons as to why this may be.
They always plateau.
May be due to exhausted nutrients, the population reaching a certain level, or lack of space.
What does light primarily affect, and how?
Affects primary producers, by affecting photosynthesis.
What is the difference between gross level and net photosynthesis? What happens if there is no net photosynthesis?
Gross level - max capacity of photosynthesis for a given species.
Net - net sugar gained per day from photosynthesis after expenditure on cellular respiration.
No net gain means no growth.
What is the light compensation point, and what value does the net gain have?
Point at which the plant breaks even on sugar production to meet cellular respiration requirements with photosynthesis.
Net gain is 0 at this point.
Do all plants have the same light compensation point?
No, it differs among species.
Describe the two types of plants in the context of sunlight.
Sun plants - grows well in full sunlight
Shade plants - work with very little light
Where are shade plants often found?
Understory.
What happens to the net photosynthesis of shade plants? Why is this so?
It will eventually plateau. Does so due to negative feedback, where more sugar is made than can be transported back, essentially stalling.
What is the net photosynthesis like in sun plants? Do they require more or less light to achieve the light compensation point compared to shade plants? Explain why.
Net photosynthesis increases almost linearly.
They need more light than shade plants to reach the light compensation point. This is because they need energy to uptake nutrients through their roots, as well as reflecting light.
What conditions are sun plants adapted to live in? Why do they not survive in low light conditions? What will happen if you put a shade plant into a high light intensity condition (ie a desert)?
Sun plants are adapted to live in desert-like conditions with high light intensity.
When put into low light, too much light is reflected due to their adaptations, and will die.
Shade plants cannot reflect enough light, and will die under high light intensity.
What are the leaves like for shade plants vs a sun plant?
Shade plants - often thin, soft leaves
Sun plants - often thick, hard leaves
How can the leaf hardness of sun plants explain their high light requirement?
Their leaves are hard due to the sclerenchyma cells, which are dead.
As they are dead, no photosynthesis occurs, requiring them to be exposed to more sunlight.
How can temperature affect an organism’s lifecycle?
Some species require certain temperatures to complete a lifecycle.
Is the optimum temperature of a species a good guide to its tolerance? Give an example.
No. Thermophilic fungi exist in Antarctica, that grow well at 45*C.
Does the region where an organism live act as a good guide to its optimum requirements (on ie temperature)?
No. Thermophilic fungi exist in Antarctica, that grow better at 45*C.
Where do C4 plants usually live, and how are the different to C3 plants?
Hotter conditions. Are able to store carbon in an intermediate step, and use later on if the temperature is too hot.
C3 cannot do this in hot conditions, and will lose too much water trying to get CO2.
What affects water availability?
Salinity.
Name 3 ways a plant can minimise water output/loss.
Waxy cuticle
Hairy surfaces
Sunken stomata
What are 2 ways some can species fight for water?
Underground through their roots, may produce toxic substances.
Plants may outgrow others, by pushing them to understory, and more photosynthesis through higher canopy cover, allowing deeper roots
Order the following from most water, to least: Open forest Mallee Desert Grasslands Shrublands (low and tall) Rainforest Closed forest
Rainforest Closed forest Open forest Mallee Shrublands (tall, then low) Grasslands Desert
Are high wet conditions always favourable?
No, some species are susceptible to diseases like fungi/bacteria.
What are some adaptations that plants and animals can have to high salinity conditions?
Plants - salt glands on their surface to excrete the salt they uptake.
Some animals have salt glands on their beaks that concentrate and excrete salt.
