Lecture 3 - RH

Question 1

What is the gross level and nett level of photosynthesis?

Answer 1

Gross level is the maximum capacity of photosynthesis for a particular species of plant.

Nett is the gross photosynthesis minus consumption of biomass during respiration.

Question 2

What are the environmental factors that affect ecosystems?

Answer 2

Light

Temperature

Water

Wind

Nutrients

Slope and aspect

Question 3

What is a sun plant and a shade plant?

Answer 3

Shade plants have low light compensation points and so can produce carbs from little light. (usually found in the understorey)

Sun plants need lots of sunlight and have high nett photosynthetic rates.

Question 4

What are leaves like in sun and shade plants?

Answer 4

Sun plants have thick and hard leaves.

Shade plants have thin and soft leaves

Question 5

What causes leaf cells to be hard in sun plants?

Answer 5

sclerenchyma cells

Question 6

How can temperature influence an ecosystem?

Answer 6

Limiting temperatures can influence life cycle

Optimum temperature for some plants allow them to produce their greatest biomass

Question 7

Is the temperature of the environment a good indication of optimum temperature?

Answer 7

Where an organism grows is not necessarily a good indication of its optimum temperature

Question 8

What is the difference between a photosynthesis vs leaf temperature curve that describes a plant adapted to hot environment (C4 plants) and a plant adapted to cold environments (C3 plants)?

Answer 8

A cool adapted plant has a large optimum range of temperatures which drops off at a certain high temperature.

A hot adapted plant has a small range of optimal temperatures and photosynthesis increases constantly until the temperature is too high

Question 9

What is the difference between C3 and C4 plants?

Answer 9

Carbon dioxide is stored in C4 plants but not in C3 plants.

C4 plants photosynthesize at night rather than during the day to avoid losing water.

Question 10

What are the important aspects of water taken into account when thinking about ecosystems?

Answer 10

Rainfall + evapotranspiration

Salinity

Each species has a minimum water demand

Balance between availability in the soil

Question 11

How do plant species minimise output?

Answer 11

Waxy cuticle and hairy surfaces

Question 12

What happens to species living in areas with lots of available water?

Answer 12

More species can cope but there is more competition as well

Question 13

Name forests from most water to least water:

Answer 13

Rainforest -> Closed forest -> Open forest -> Mallee

Question 14

Name shrubland from most water to least:

Answer 14

Tall -> Low

Question 15

What are the Australian multi-stemmed eucalypts?

Answer 15

Mallee

Snow Gum

Question 16

Why is salinity such an issue with water uptake by plants?

Answer 16

It affects the bioavailability of water through a decrease in the osmotic pressure into the roots thus slowing rate of water uptake.

Question 17

What kind of species dominate salty habitats?

Answer 17

Salt-tolerant species dominate salty habitats

Question 18

What are the effects of wind on plants?

Answer 18

Affects rate of transpiration

Causes disease

Causes sand to move onto leaves

Windy habitats are also stressful habitats

Question 19

is sand high in nutrients?

Answer 19

No

Question 20

How is the ability of soil to store nutrients measured?

Answer 20

Cation Exchange capacity (CEC)

Question 21

How does soil type affect vegetation?

Answer 21

Plants are adapted to a certain amount of nutrients so there are abrupt changes in vegetation with changes in soil type

Question 22

What is a mesophytic habitat?

Answer 22

A non-extreme environment with relatively good levels of water etc

Question 23

What is the biodiversity like in mesophytic habitats?

Answer 23

Very low due to competition resulting in one dominant species

Question 24

How does slope and aspect affect ecosystems?

Answer 24

Interacts with water via drainage. Less water in the higher areas compared to lower areas

Any slope facing north gets more sun then slops facing west

More wind on top of the slope then on the bottom

Question 25

What are some biotic factors that are relevant to ecosystems?

Answer 25

Competition between like species

Predation: lots of prey = lots of predators