Extreme Biology Flashcards
What are the extreme environments plants may face?
- Cold
- Drought
- Heat
- Light
- Salinity
- Flooding
- Nitrogen poverty
- Wind
- Loneliness
Leaves tend to become hot in daylight due to solar radiation how do they adapt to avoid overheating?
- Solar radiation ~1kW per m2
- A broad leaf in full sun, windless, can be ~20ºC hotter than local air
- Leaf shape helps to prevent overheating
- Plants adjust leaf size within limits
How does leaf size vary depending on heat in the envieronment?
- Small for extremes of dryness, heat, drought, and cold
- Large (to maximise light harvesting) where there is sufficient water for cooling and warm enough to avoid excessive radiative cooling.
What is an Ephermal plant?
Ephemeral, in botany, any short-lived plant, usually one that has one or more generations per year, growing only during favourable periods (as when adequate moisture is available) and passing the unfavourable periods in the form of seeds. The seed coats of some species contain a growth inhibitor that can be washed off only by a copious quantity of water, thus preventing germination after only a brief shower.
- The seeds are long lived and highly resistant
- Rapid germination and rapid progression through life cycle of growth, flowering, seed setting and death.
- They are not particularly drought resistant
What is Cryptobiosis?
Cryptobiosis is defined as the state of organism when it shows no visible signs of life and when its metabolic activity becomes hardly measurable, or comes reversibly to a standstill.
Cryptobiosis is a generic term for ametabolism, and can be further divided into five categories based on factors inducing them: cryobiosis (induced by freezing), thermobiosis (low and high temperatures), osmobiosis (high osmolarity), anhydrobiosis (lack of water) and anoxybiosis (lack of oxygen).
What are Adaptors? Specifically Poikilohydric plants?
Small plants specialised to survive drought period.
Poikilohydric plants are those in which water status is completely dependent on their environment (Walter 1931) so that, in terrestrial habitats, the water vapor partial pressure of the plant body comes into equilibrium with the humidity of the atmosphere.
How do Adaptors utilise cryptobiosis?
Dehydrates, shrivels, photosynthetically inactive in drought - regrows from dormant root and shoot when watered.
Dehydration protection response – accumulation of sucrose and trehalose to protect membranes and proteins from denaturation.
What’s an example of a resistor?
Phreatophytes are an example of a resistor.
What are Phreatophytes?
- Deep-rooted plants that obtain a significant portion of their water from the phreatic zone (zone of saturation).
- Modifications to root structures.
- Access water from deep soil.
What are some examples of phreatophytes?
The creosote bush, mesquite plant.
What are some adaotations of phreatophytes?
Tiny leaves (reduced water loss, more efficient heat loss?).
Stomata closed during day.
Rapid rehydration and flowering when water becomes available.
What is desertification?
– well established plants may survive but seedlings won’t (e.g. large Sahara trees).
What is the oldest phreatophyte?
“King Clone” is thought to be the oldest creosote bush ring in the Mojave Desert.
The ring is estimated to be 11,700 years old, making it one of the oldest living organisms on Earth.
This single clonal colony plant of Larrea tridentata reaches up to 20 m in diameter, with an average diameter of 14 m.
What are Xerophytes?
Arid and desert plants
Usually have small leaves (or needle leaves)
Thickened leaves or stems for water storage also double as a heat buffer
They are leaf and stem succulents.
What are leaf and stem succulents?
Stem succulents: (most of which are cacti) plants the have swollen, moisture-retaining stems.
Leaf succulents: Plants that have foliage but often lack a stem, whereas cacti and other stem succulents have a swollen stem but mostly lack leaves. (e.g. Echeveria laui or many vygies, i.e. members of the family Mesembryanthemaceae – commonly referred to as mesembs)
(e.g. Pachypodium namaquanum)
Give an overview of Cacti and their adaptations to their environment
- Restricted to the Americas
- Distinctive areolae.
- Leaves reduced to non-photosynthetic protective spines.
- Photosynthesis in stems, not leaves.
- Reduced stomata.
- Waxy, hairy, or spiny outer surface
- Humid micro-habitat.
- Compact, reduced, cushion-like, columnar, or spherical growth form.
- Reduction in surface area:volume - reduced water loss.
- Highly impervious outer cuticle.
- Roots very near the surface of the soil
- Rapid absorption of limited and periodic water.
- Ribs enable rapid increase in plant volume.
- Ribs decrease surface area exposed to the sun.
- Stomata tend to be in the rib valleys.
How do cacti protect growing tip from overhead sun?
Cacti have a dense crown to prevent growing tip from overhead sun.
What conditions do high altitude cacti face?
- Desert conditions
- Sub-zero temperatures at night
- Excessive solar radiation (UV)
How does Protective Pubescence protect cacti?
Protective pubescence
- Scatters light
- Reduction in light reaching stem (up to 56%)
- No great reduction in CO2 entry
- Still, moister air near stem surface à reduced water loss
- Limits heat loss at night from re-radiation
- Protection from herbivores (physical barrier, spines and detachable irritants)
- Reduces access to spores of pathogens
What are Lithops?
- Lithops are considered ‘stone plants’/’window plants’
- Native to South Africa
- Consist of paired fleshy leaves that guide sunlight through plant to photosyntetic cells.
- Protected from heat and herbivores.
Longitudinial section of a Lithop plant
Give a brief overview of the Compass plant and how it is adaoted to reduce heat and water loss.
- Compass plant AKA Silphium laciniatum
- Native to Ontario, central United States, New Mexico.
- Large leaves held vertically, tips pointing north or south, upper and lower surfaces of the blades facing east or west.
- Newly emerging leaf grows in a random direction - within two or three weeks it twists on its petiole into a vertical position.
- Sun’s position in the early morning hours influences the twisting orientation.
- This orientation reduces the amount of solar radiation on leaf surface.
- Vertical leaves facing east-west have higher water use efficiency than horizontal or north-south-facing blades.
- Settlers on the Great Plains could make their way in the dark by feeling of the leaves.
Give a brief overview of C4 metabolism.
- Evolved independently in several lineages of vascular plants. Many grasses.
- Evolved from C3 metabolism, the first step in the Calvin cycle.
- Named C4 because, instead of initially forming a C3 compound (pyruvate), they make a C4 compound (malate).
- Only ~3% of plant species use it, but …
- Comprise ~5% of global plant biomass, ~23% of terrestrial carbon fixation.
- Lose about half as much water per unit CO2 fixed as do C3 plants.
- System is less efficient than C3, but reduces photorespiration, saves water, copes with higher light intensities.
- Separates reactions spatially inside leaves.
RuBisCO and its role
The enzyme ribulose 1,5-bisphosphate carboxylase (Rubisco) catalyses the entry of carbon dioxide into photosynthetic metabolism, provides acceptor molecules that consume the products of the light reactions of photosynthesis, and regulates the pool sizes of important photosynthetic intermediates.
What is the issue with RuBisCO?
Rubisco is not very efficient at grabbing CO2, and it has an even worse problem. When the concentration of CO2 in the air inside the leaf falls too low, Rubisco starts grabbing oxygen instead.
What is the cause of RuBisCO’s issue?
RuBisCO evolved when O2 levels in the atmosphere were much lower than today – so less selection pressure at that time to discriminate.
How have some plants overcome the issue with RuBisCO?
Compensatory mechanisms for drought conditions
Some plants have evolved a slower-acting RuBisCO with an improved ability to discriminate – but results in a 30% loss in photosynthetic efficiency.
Or, evolution of CO2-concentrating mechanisms that reduce O2 concentration - as in cyanobacteria and C4 plants – higher catalytic rates, lower CO2 affinity.
Give an overview of how C3 and C4 reactions in space
- CO2 pumps increase concentration internally.
- RuBisCO is sensitive to O2
- Generate an environment high in CO2 in bundle sheet cells.
- Malate synthesised in mesophyll cells – diffuses to bundle sheath cells.
- Less energy efficient than C3, but overall advantage because reduces wasteful oxygenation of RuBisCO.
Why can’t C3 plants grow in very hot areas?
C3 plants cannot grow in very hot areas because RuBisCO incorporates more oxygen into RuBisCO as temperatures increase.
CO2 for RuBisCO drawn from malate rather than directly from the air.
What is Crassulacean Acid Metabolism?
- A form of C4 metabolism, but separates reactions by time (and space).
- Stomata open at night.
- CO2 acquired and reacts with phosphoenolpyruvate.
- Malic acid is stored.
- During daylight, stomata are tightly closed.
- CO2 is released from malic acid.
- CO2 incorporated into Calvin cycle.
Diagram of CAM and speration of C3 and C4 reactions in time
What is a halophyte?
A plant adapted to growing in saline conditions, as in a salt marsh.
What ares some specialised organs in a halophyte?
- Salt glands
- Slat bladders
What do halophytes do when they encounter excess salt or drought?
Shifts from C3 to C4 (CAM) metabolism when it encounters drought or excess salt.
What are pneumatophores?
They are specialized aerial roots enabling plant roots access to oxygen in waterlogged habitats.
What genes did seagrass lose when it adapted to life in sea as opposed to land?
What genes did seagrass regain?
Lost all genes for:
- Stomata formation
- UV protection
- Sensing far red light
- Volatile turpenes
Regained genes for:
- Cell wall components for osmotic control
What’s an adaptation of Nitrogen poverty in plants?
Carnivorous plants are predatory flowering plants that kill animals in order to derive nutrition from their bodies. They share three attributes that operate together and separate them from other plants. Carnivorous plants: Capture and kill prey. Have a mechanism to facilitate digestion of the prey.
How is the Artic tundra adapted for the cold?
Plants also have adapted to the Arctic tundra by developing the ability to grow under a layer of snow, to carry out photosynthesis in extremely cold temperatures, and for flowering plants, to produce flowers quickly once summer begins. A small leaf structure is another physical adaptation that helps plants survive.
Life in Rocks
What are the two native vascular plant species, growing as small clumps, south of 58ºS?
the two native vascular plant species, growing as small clumps, south of 58ºS are:
- hair grass
- pearlwort
What are the dangers of a cold environment?
- Changes in biological thermodynamic processes.
- Changes in biomolecule conformation, stability, function.
- Perturbation of normal cellular processes.
- Reduced fluidity of cell membranes - rigidification.
- Perturbation of the balance between production and neutralisation of reactive oxygen species (ROS).
- Extracellular ice crystal formation depletes water in and around cells
- freezing dehydration and associated cell membrane disruption.
- Large ice crystals grow at the expense of small crystals – ‘ice recrystallisation’.
Give some facts about Taiga
South of tundra.
Also known as boreal forest or snow forest.
Biome dominated by coniferous forests comprising mostly pines, spruces and larches – only a few angiosperm (‘broadleaved’) trees and shrubs.
Low species diversity – large stands of single species.
Earth’s largest terrestrial biome.
One third of terrestrial carbon store.
Taiga forest of Canada and Siberia
- record temperatures range from -64°C to +36°C
– spanning a full 100°C.
Carbon dioxide ice sublimes at −78.5 °C!
Some arctic pines needles and angiosperm buds can be cooled slowly to -30°C then into liquid nitrogen (-196°C) and recover alive.
How are conifers well adapted to their environment?
Conifers are well adapted to dry, cold, and altitude.
Most species are evergreen – resilient leaves, spring-ready.
Autumn shut down of photosynthesis and increase concentrations of
carotenoid pigments (e.g. zeaxanthin and lutein) to protect against light damage.
Shed snow efficiently.
Do not restart even on warm days – wait until April/May then rapid resumption of photosynthesis – forests rapidly become CO2 sinks.
How do Taiga Conifer Trees prepare for winter?
Detection of cold and/or detection of predictive seasonal changes
- temperature reduction, day length.
- induction of protective cold tolerance mechanisms and components.
Large central cell vaculole replaced by numerous small vesicles.
Starch granules disappear.
Thylakoid membranes in chloroplasts separate and become disorganised.
Changes in membrane lipid composition (e.g. desaturation of fatty acids; increased phosphatidylethanolamine, decreased phosphatidylcholine; in chloroplast membranes, increased phospholipids, reduced galactolipids).
High concentrations of oligosaccharides – promote vitrification or high viscosity in cytoplasm of freeze-dehydrated cells.
Proteins – upregulation of …
- dehydrins – bind membranes, prevent membrane-membrane interactions
- antioxidant systems
- heat shock proteins
- pathogenesis-related proteins.
How are deciduous trees adapted for seasonal dangers?
Temperate winter or tropical dry seasons.
Abscission layer forms between the leaf petiole and the stem.
Forms in the spring during active new growth of the leaf.
Layers of cells that can separate from each other.
The cells are sensitive to auxin produced by the leaf.
Sufficient auxin à abscission layer cells remain connected.
In autumn, or when under water stress, auxin from the leaf decreases or stops
à cellular elongation within the abscission layer.
Elongation of these cells break the connection between the different cell layers à leaf breaks away.
Abscission layer cells seals the break, plant does not lose sap.
Meanwhile – production of sticky, sugar-protected buds ready for spring
Diagrams of abscission zone
How are rohododendron adapted to their environment?
If a lot of cold wind blows past your rhododendron in the winter, it will curl its leaves inward so less leaf surface is exposed; the plant’s trying to keep water from evaporating out of its leaves.
How does Crown drag affect Oak and Pine trees?
Crown drag – strongest in broad-leaved trees – advantage to be deciduous.
Oak-type tree – dense, heavy trunk, limited sway, broad, stiff root base.
Pine-type tree – lighter trunk, more sway, deep tap root.
How has rainforest soil affected the roots of trees in the rainforest?
Most rainforest soil is nutrient-poor.
Nutrients available largely near soil surface.
Rainforest trees therefore tend to have very shallow roots.
- Buttress roots
How ado leaves aid in lessening the effects of crown drag?
Leaves need to protect themselves and the tree’s crown by reducing drag.
They twist, curl and fold.
Small leaves and flexible branches help.
What contributes to loneliness in a plant?
- Distant colonisation
- Devastated land
- (fire, vulcanism)
- Wide separation
What is a method of combatting loneliness in a tropical rainforest?
An ecosystem type that occurs between approx. latitudes 28 º N or S of the equator.
More biodiverse than anywhere else on land (compare with tundra).
How does a tree find a mate in a tropical rainforest?
Conspecifics and potential plant mates are usually far away.
Need to synchronise flowering.
But how? What cues to use?
In temperate and polar regions
plants can use seasonal daylength and/or temperature changes.
Where do extremophile prokaryotes have their origins?
Extremophile prokaryotes have their origins in the Archean Aeon (Eon)
What are the planetary extremes that organisms face?
- pH
- High temperatures
- Radiation
- Pressure
- Salinity
- Freeze Tolerance
- Desiccation
Where does most life on earth lie?
Most life is underground.
With the No. of microbes on earth being around 4 x 1030 at least.
Give a brief overview of the nematodes
- ‘Worms from Hell’ South African mines.
- Deep subsurface biosphere > 3 km into the Earth’s crust.
- Detected at 0.9–3.6 km deep - Halicephalobus mephisto.
- Tolerate high temperatures - Reproduce asexually - Feed upon subsurface bacteria.
- 14C data - nematodes reside in 3,000–12,000-year-old palaeometeoric water.
- Such nematode species should be found in other deep hypoxic settings.
- May control the microbial population by grazing on fracture surface biofilm patches.
- Multicellular life in the deep subsurface of the Earth has implications for the search for subsurface life on other planets in our Solar System.
- (anhydrobiosis dauer larvae)
What are chemoautotrophs?
Chemoautotrophs
- Convert the heat, methane, and sulphur compounds provided by black smokers into biochemically useful energy through chemosynthesis.
- More complex life forms, such as clams and tubeworms, feed on these organisms.
What species can survive space?
Cyanobacterium
What is the driest place on earth?
Atacama is the driest place on earth
Give an overview of the tardigrade
“Water bears”, “space bears”, or “moss piglets”
Kingdom Animalia; Phylum Tardigrada
Some can withstand –
- temperatures down to 1°K (−272°C).
- temperatures up to 420°K (150°C) for several minutes.
- pressures about 6x greater than found in the deepest ocean trenches.
- ionizing radiation doses hundreds of times higher than lethal for humans.
- vacuum of outer space.
- can go without food or water for >30 years,
- drying out to the point where they are 3% or less water,
- successfully rehydrate, forage, and reproduce.
Diagram of the different sources of metabolism.
Diagram detailing how the different lipid classes confer shape
- When exposed to stress the heterogeneous mixtures (rafts) of different lipids can phase separate to form pools of a single class
- Can lead to a physical change in the bilayer structure
- Inverted micelles and Hexagonal II (HexII) can form → leakage .
Inverted micelles – head groups face inwards
Give the Cell Surface and membrane structure of some Archaeans
Most archaea possess a cell wall.
The wall is assembled from surface-layer proteins, which form an “S-layer”.
An S-layer is a rigid array of protein molecules that cover the outside of the cell (like chain mail).
This layer provides both chemical and physical protection, and can prevent macromolecules from contacting the cell membrane.
Describe the process of ubiquitination
Damaged or misfolded proteins are first labelled for destruction by ubiquitination.
A sequence of three enzymes targets causes covalent attachment of ubiquitins to a lysine in the protein.
A target protein must be labelled with at least four ubiquitin monomers (in the form of a polyubiquitin chain; “polyubiquitination”) before it is recognized by the lid proteasome.
Inside the proteasome a protein is cleaved by an enzyme with a threonine in its active site.
What are the three main strategies for combatting hear and dryness in animals?
The three groups are:
- Evaders
- Evaporators
- Endurers
There is a correlation between the rat of evaoporation and body mass.
How do sidewinding snakes adapt to heat?
Rather than moving in the direction of the head as do other snakes (A), sidewinding snakes move sideways both on level ground (B) and up slopes (C). Marvi et al. show that when snakes sidewind up a slope, they increase the body length that is in contact with the ground, thereby reducing slip.
Labelled Diagram of body mass vs estimated evaporation as a percentage of body mass.
The kangaroo rat has a small body ad will die at 10-20% water loss, so it opts to avoid heat in burrows.
Camels have large bodies and can’t evade the heat. Their water expenditure for cooling is limited.
Hence thick insulation and body temperature tolerance.
Graph represents evaporative cooling necessary to maintain body temperature steady for 1 hour.
How do sea animals adapt to the colder temperatures?
Some sea animals such as penguins and fur seals have an external layer of insulation (feathers or fur), but most species of sea mammal (such as whales and dolphins) do not. Instead they rely on a thick layer of internal insulation that doubles as a food store and streamlining. Here is a cross section of a frozen seal showing the depth of the fat-rich blubber layer, amounting to about one third of the radius from the core of the animal. And even there the composition of the blubber layer changes from inside to outside in order to retain the physical properties of the lipids in cell membranes throughout, as explained in the slide. Incidentally, the blubber layer of seals that are preyed upon by polar bears are crucial to the survival of the bears – fat is a high energy store per gram of tissue, and the bears need to acquire it to fuel the heat production they need to survive in the sea or in land or ice environments that will be below freezing for several months.
What is the problem with good insulation and how is it combatted?
Possession of good insulation can present the problem of overheating when the external temperature changes or excess heat is produced internally through exercise, as with migrating, hunting or escape. Polar bears, for instance, can overheat if forced to engage in a long chase. But, insulation layers can be tuned by reducing or increasing the dept of fur or feather layers using erector muscles in the skin – such as in goose pimples or goose bumps in humans, which are contracted erector muscles attached to hairs (not much use in humans now). Alternatively, peripheral blood flow can be increased to heat the external surface and thereby lose heat, or reduced to conserve heat. This works by muscular contraction or relaxation of blood vessels to open or close peripheral blood vessels or shunts as illustrated in the slide.
How do birds conserve heat?
Birds tend to have very thin legs, so have a very high surface to volume ratios. They consequently exhibit highly efficient countercurrent heat exchangers as illustrated here in a cross section of a bird’s leg, with the central artery with its muscular wall apposed to the thin-walled veins.
How does the need for hibernation change according to mass of the animal?
As one goes from small to large animals then their metabolic rate per gram of tissue goes down. So, less expenditure of body reserves is required to maintain their body temperatures. Also, large animals have small surface:volume ratios, so lose less heat, such that they can survive a winter living on their stores of fat – brown bears, for instance, can double their body weights in a feeding frenzy before winter. And, yes, when bears den for the winter their body temperatures do not fall to the levels achieved by hibernating ground squirrels or hamsters.
How do different animals breathe?
- Amphibians are positive pressure breathers.
- Most non-avian reptiles, birds and mammals are negative pressure breathers, using rib ventilation.
- Mammals have elaborate, alveolated lungs to increase surface area for gas exchange, but are still essentially simple bags.
- Birds have a flow-through system in their lungs so that only fresh/unused air passes over absorptive surfaces.
Erythrocytosis in Andeans
Enhanced Oxygen loading in blood of andeasn and tibetans
