Unit 2 - Chapter 2 - Abiotic Conditions

Question 1

Question 2

Types of Abiotic Conditions that organisms encounter?

Answer 2

1. Water
2. Lack of Water
3. temperature (sunlight)
4. soil
5. O2 levels
6. In aquatic: salinity & ocean currents

Animals and plants respond to these challenges in different ways..Terrestrial and Aquatic environments impose challenges on the organisms that live there.

Question 3

Plants:

Resources that Plants need?

Answer 3

• Light: absorb in 400-700 nm range (about the same as ‘visible spectrum’ of humans).
• It’s called Photosynthetically Active Radiation. Outside of this range is useless radiation for plants!
• always light —> chemical energy
• 6CO2 + 12H2O –> C6H12O6 + 6O2 + H2O
• Light availability? direct influence on rate of photosynthesis
• can’t do photosynthesis in the dark THEREFORE cellular respiration is done

Question 4

What is the Light Compensation Point (LCP)?

Answer 4

• light level at which the plant takes up CO2 (and equals the loss of CO2 in respiration)
• Increase light saturation, Increase the photosynthetic activity? NO. There is a Light Saturation Point (the intensity at which additional increases in light do not increase photo- synthesis) that occurs above the photosynthetically active radiation (PAR)
• Decrease will occur? YES. called photoinhibition (rate of photosynthesis will decrease as PAR exceeds this saturation point.

Question 5

Patterns of light seen in Aquatic environments?

Answer 5

1. littoral zone: plants are there, so light is reaching to the bottom (at least the top 200 m), the ‘continental shelf’ area
2. limnetic zone: no plants, no light really, deep ocean area.
3. benthic area : bottom of ocean, no light!

How do plants adapt to grab this light in the water? long stalks with leaves floating on the top of the water. or migrates around the water in order to grab that light.

Question 6

Shade tolerant plants and their adaptions?

Sun-loving plants and their adaptions?

Answer 6

SHADE-LOVER:
1. Produce less RUBISCO (carbon-fixation enzyme in chloroplasts)
2. Use less CO2 in the dark
3. Lower max rate of photosynthesis
4. Uses less daily energy to keep itself alive BUT can only use a lower level of light AND has a lower maximum level of photosynthesis.
5. lower LCP (light compensation point) -takes less light to start capturing CO2 and start the photosynthesis process.

SUN-LOVERS:
1. Bloom early
2. Grow taller
3. Has higher photosynthetical active radiation (PAR) levels
4. Higher levels of Rubisco
BUT spends more energy to keep itself alive during day and night!

Question 7

Types of adaptations for terrestrial plants in high light conditions?

Answer 7

• water constraints
• food contraints
• has to deal with the high temperatures.

Question 8

Transpiration?

Answer 8

when the stomata is open, water vapour in the leaf diffuses out.

Depends on the diffusion gradient and stomatal conduction (diffusion of gas, such as CO2, H2O vapor, and O2, through the stomata of a plant. It also functions as the measure of stomatal opening in response to environmental conditions) of H2O vapour.

HIGH RATE OF TRANSPIRATION? occurs in dry & arid conditions (dry, hot soil and air)

Adaptations of plants in hot areas?
1. roots (tap or shallow fibrous)
2. leaves (curly, broad, needle)
3. wax on those leaves (cuticle)
4. Less stomata/more stomata or sunken stomata or smaller stomata
5. pubescence on the leaves - hairs reflect light in order to keep leaves cooler
6. being more upright and shorter in size
7. having lobes on leaves (like oaks) which decrease surface area but also leaves space between those lobes
8. Some plants may have essential oils that deter pests. Limits having leaves or stems punctured by pests and this limits H2O, CO2, O2 loss.

Adaptions a result of SELECTIVE PRESSURES like temperature. And PHENOTYPIC PLASTICITY and ACCLIMATION does occur within a species in order to maximise life in different seasons/temps.

The balance between photosynthesis and transpiration is an important evolutionary constraint in terrestrial plants. What constraint? drier soils, less photosynthesis occuring bc plants can’t keep up the levels of transpiration.

Rainy day? Humid day? LESS transpiration (also less O2 and CO2 going in and out of those stomata)
Windy day? Sunny day? Dry day? MORE transpiration. Also the plants open the stomata to cool themselves down!

Question 9

C3,
C4,
CAM ,
photosynthesis types?

Adaptations?

Answer 9

1. C3: 89% of plants, typical habitat (everywhere), plants (wheat, tomatoes, fruit, rice), bundle sheath cells not present/without chloraplasts), optimal temp (25-35 C). photosythensesis takes place in mesophyll cells with chloraplasts. Does normal photosynthesis – normal Calvin Cycle w/ CO2 uptake.
2. C4: <1% of plants, typical habitat (grasslands, deserts), plants (corn, sugar cane), bundle sheath cells (directly around xylem/phloem) with chloraplasts AND mesophyll cells with chloroplasts, (T) CO2 is incorporated into organic acids in the mesophyll cells where C4 molecules, then transported to bundle sheath cells. Then Calvin Cycle is done. Good at optimizing Calvin Cycle under dry conditions.
3. CAM: 10 % of plants, optimal temp (35-45 C), plants (pineapple, prickly pear), habitat (humid areas and tropics), succulence of plant cells and tissues, optimal temp (45 C+), occurs in mesophylls but at night only when CO2 fixation occurs. (T) Stomata opens up at night, when less transpiration is occurring, CO2 is taken up in organic acids in mesophyll, then stored until morning. During the day, CO2 is transported to bundle sheath cells during the day because of sun and then Calvin Cycle is completed. FAR FAR more efficient then C3 and C4 and can handle even drier conditions.

For #2 and #3, they are specialised in the way they carry out the Calvin Cycle. Not the cycle itself, but HOW the CO2 is transported to the location where the Calvin Cycle is done. So stomata can be closed during the day time, where water loss is occurring the most.

Question 10

Answer 10

Closing the stomata
* reduces H2O loss
* reduces CO2 diffusion through the leaf
* increases heat of plant though

Question 11

Transpiration?

Answer 11

(T) Temperature closely associated with availability of H2O b/c at higher temperatures, there are higher rates of evapouration. Lower temps, less evapouration. Air temp increases, saturation vapour rises, rate of transpiration rises.

Higher temps, warmer air holds more H2O vapour. With higher temps, humidity decreases and the stomata open. High humidity, stomata close.

Loss of water is also needed to cool off the leaves. If close stomata, not cool off as well. Heat stress.

Question 12

Adaptation that enables plants to cool their leaves in hot temps?

Answer 12

Morphological :

1. lobes/leaf shape
2. edges vs surface area

Due to evolution? YES. standard differences in the shapes of leaves. Selective pressures of temperatures on leaves over time.

Question 13

Acclimation?

Answer 13

• NOT genetic changes
• THEY ARE phenotypic changes due to environmental pressures and conditions.
• these are not evolutionary changes

Question 14

There are always ‘trade-offs’?
Examples.

Answer 14

(T) an inescapable compromise between a couple of traits. Can optimise one trait only while the other is just okay.

<OK>

1. **Cactus**: great at storing and tolerating extremely high heat, but lacks continuous flowers and leaves
2. **Shorepine** (*Pinus monticola*): can live in temperate rainforest, tolerant to salty coastline, BUT can't tolerate high & dry heat.

**KEY**: a plant can either be really good at photosynthesis, but it severely drops off in dry conditions (**red alder** below) why? they can't *maintain* their level or transpiration. Drier soils = less photosynthesis.

_OR_

Can tolerate drier soils longer *but* overall, is not very good at photosynthesis (the **oak**)

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Question 15

PAGE 7:

What types of environmental variables might animals deal with?

Answer 15

temperatures
sunlight
O2

Question 16

An animal can respond to environmental changes in 2 different ways:
1. CONFORM
2. REGULATE

Answer 16

1. Conformers : changes in the external environment cause parallel changes in the body – it conforms to the environment. Internal conditions = external conditions. Narrower range the animal can live in though. ex: amphibians, reptiles, fishes, insects
2. Regulators : internal conditions ≠ external conditions. Despite variable conditions outside, the organism can maintain it’s internal environment. Can live in a larger range of environments. ex: mammals & birds
3. Conformer/Regulator : animals may use different strategies under different environmental conditions. Regulates one feature, but conforms with another.

A species may regulate with respect to one feature but conform to another.

Question 17

What is meant by Homeostasis?

Answer 17

• maintenance of a relatively constant internal environment in a varying external environment.
• It’s a state for an organism to be in for survival

Question 18

1ST EXAMPLE: how animals regulate/conform —

Why do animals require O2?

What types of adaptations are there for animals have for low O2?

Answer 18

• cellular respiration
• last step in cellular respiration in order for ATP to be produced.
• More active, more O2.

Less O2 ? water, higher altitudes
Less O2 in aquatic? bottom of ocean, bottom of deep lakes, areas of still, stagnant water, areas with more decomposition, warmer water, areas with less plants and limited photosynthesis.

Adaptations? lower metabolism, do less activity (less energy needed), mutualism

EX : Salmon will struggle and die off in high temps 20-25C. As body heats up, speed up chemical reactions, need more ATP, need more O2….but warm water has less O2.

Question 19

2nd EXAMPLE: how animals conform/regulate –

Osmoregulation

Answer 19

Water balance is the balance between the uptake and the loss of water with the surrounding environment.

Osmosis.

Food and water is where animals get their H2O. Sometimes water is absorbed on skin.

ADD: food, water

LOSE: digesting food, breathing, opening mouths to make any sound, sweating,

AQUATIC: mouth, gills

Freshwater animals: they have more salt inside than the water, risk of taking on too much water and losing too much salt, they need to get rid of excess water.

Marine Animalsregulate: water outside has more salt, risk of losing their water.

Marine Animals conformers : NO salt or water gain or loss

Question 20

Hypotonic environment?
Hypertonic environment?

Answer 20

1. “If an animal cell is placed in a hypertonic solution, water molecules will move from the animal cell into the hypertonic solution, This causes the animal cell to shrink and reduce in size”
2. “If animal and plant cells are kept in a hypotonic solution then endosmosis will occur. Endosmosis is a process in which the water molecules move from outside of the cell of lower solute concentration to the inside of the cell of higher solute concentration through the cell membrane or cell wall.”

Question 21

Nitrogenous Waste:

Breakdown of proteins.

Answer 21

1. Ammonia: fish. can dilute into water because it’s incredibly toxic.
2. Urea : humans/mammals. hold onto urea and dilute it with our own water. but we lose water at the same time.
3. Uric Acid : bird’s poop, not mixed with water so no water loss. Also, good because they sit on eggs so they can’t have water/toxins sitting on the eggs. Also, they don’t want to have a bladder carrying around extra liquid while flyng all day.

Question 22

Adaptations to dry areas?

Answer 22

• migrate to another cooler area
• estivation: toads hide underground during the hot times
• animals halt metabolism during dry areas
• have high efficiency rates at extracting water from food, even seeds.

Question 23

3rd EXAMPLE:

Poikilo-therms?
Homeo-therms?

Ectotherms?
Endotherms?

Answer 23

1. Poikilotherms : (variable body temperature) Body temperature varies with the temperature of their environment, as they lack the ability to internally regulate. They do this by behavioural means, such as basking in the sun on a rock (Ex: reptiles & fish) Not true thermoconformers.

1 a) ECTOTHERMY: process of primarily relying on external environment for heat source (or releasing heat to environment) Again, behavioural adapting. Most ectotherms are poikilotherms, but not all poikilotherms are ectotherms.

2. Homeotherms - (constant body temperature regardless of external environment). Have the ability to internally regulate temperature within a narrow range, by its metabolic activity. Generally have insulation (fur, fat, feathers). Need efficient respiratory and cardiovascular systems to provide blood to tissues. (Ex: Humans, mammals, birds). The ‘thermoneutral zone’ is the temp range in which homeothermic organisms can maintain their body temp’s without expending additional enegy to cool down/warm up. Metabolic heat production and heat loss are balanced, resulting in minimal energy expenditure to maintain a stable body temp. This range varies among organisms and is influenced by body size, metabolic rate, insulation & environmental conditions. The optimal body temp is where the organim functions most efficiently, and conserves the most energy.

2 b) ENDOTHERMY: process of relying on internal body to make heat, so again, done metabolically. But allocate more energy to metabolism instead of making mass. Small endotherms have more surface area, thus more heat is lost to the environent. (Ex: mammals, birds)

Only true thermoconformers are animals that live in environments with almost no variation in temperature such as the deep ocean.

Categories are not absolute and some organisms exhibit characteristics of both categories. Ex: some reptiles can temporarily increase their body temperature through behavioural means (endothermy + ectothermy)

Question 24

Heterothemic:
What is meant by torpor?

What is meant by hibernation?

Answer 24

Smaller homeothermic animals often become heterothermic to reduce metabolic costs when they are inactive, by doing these 2 things:

1. TORPOR: the dropping of the body temperature to approximately ambient temp for part of a day.
2. HIBERNATION: the dropping of the body temperature to near ambient temperature for a long period of time during the winter. When the animal becomes active again, body temperature quickly returns back to normal. Instead of a daily cycle, like torpor, this is seasonal.

Question 25

What is meant by counter current heat exchange system?

Answer 25

is an arrangement of blood vessels in which heat flows from warmer to cooler blood, usually reducing heat loss. Some animals use body insulation and evaporative mechanisms, such as sweating and panting, in body temperature regulation.

EX: dolphins (in flippers), storks/cranes (in long legs and feet), geese (in legs and feet)