Ecology (CQC&SCR&JBW) Flashcards
What is a habitat
A habitat is the place where an organism lives. It is a description of the geographical location, the type of ecosystem, the physical location within the ecosystem and both the physical and chemical conditions. It usually refers to one species but the habitat of one organism, a whole population or a whole community.
Biotic and abiotic factors
The environment of an organism is everything that is around it. This includes other living organisms and non-living materials such as air, water and rock. Living things are referred to as biotic factors and non-living things are referred to as abiotic factors. Biotic factors dominate in ecosystems where there are dense communities of organisms. All organisms are adapted to their abiotic environment
what are the challenges facing plants in sand dunes
Sand dunes are accumulations of wind-blown sand at the top of beaches. Sand on beach dunes may contain high salt concentrations, hindering water uptake by osmosis. These are the challenges for plants on beach dunes:
- tolerance of sand accumulation
- tolerance of high salt concentrations
- water conservation
Adaptations of grasses in sand dunes (Lyme grass)
Special adaptations are required to meet these challenges. Grasses are the dominant plant in this habitat in many parts of the world. Lyme grass occurs where sand is accumulating at the seaward edge of the dunes in North America. It has rhizomes (underground stems) that grow upwards as sand accumulates and extend deep into the dune to obtain water, and provide extra stability. They also have:
- A thick waxy cuticle to reduce transpiration
- Fructans (a carbohydrate) which accumulates in leaf root cells, which increases osmotic potential and thus water uptake
- Stomata at the base of hairy furrows humid air is trapped, even in windy conditions (reduces water loss by transpiration)
- During droughts tough sclerenchyma tissue near one leaf surface prevents wilting and causes the leaf to roll up, creating a humid chamber which is less exposed to wind (also reduces transpiration)
Challenges of mangrove trees
Mangrove swamps develop on the coast in the tropics and subtropics where there are sheltered conditions and mud accumulates. These swamps are flooded with seawater at high tide. The dominant species are trees.
These are the environmental challenges of mangrove swamps:
- Waterlogged anaerobic soils which make it difficult for tree roots to obtain the oxygen they need for cell respiration
- High salt concentrations which tend to draw water out of cells by osmosis to prevent water uptake. The salt concentration of the mud can be twice as high as that of seawater. This is due to the daily flooding with seawater and evaporation concentrating the salt in the mud.
Adaptations of mangrove trees
The main adaptations are:
- Large buoyant seeds produced by trees which drop into the water and are dispersed by ocean currents
- Salt glands on the leaves which secrete excess salt
- Stilt roots which grow out in a downward arch from the central trunk to buttress the tree in the soft mud
- Cable roots which grow close to the soil surface where there is most oxygen
- Pneumatophores, vertical root branches that grow up into the air and can absorb oxygen for roots to use in the anaerobic soil.
- Root epidermis which is coated in suberin (cork) which reduces permeability to salt so prevents excessive uptake
- Root and leaf cells which contain mineral ions and carbon compounds such as mannitol, which increase osmotic potential, enabling water absorption from the very saline environment.
what is species distribution?
The distribution of a species is where it lives in the world. Distribution is limited by abiotic factors. The adaptations of plants and animals suit them for living in some physical environments but not others.
what are the abiotic factors affecting plant and animal distribution?
Plant distribution:
- temperature
- water availability
- light intensity
- soil pH
- soil salinity
- availability of mineral nutrients
Animal distribution:
- water availability
- temperature
The adaptations of species give it ranges of tolerance
Formation of coral reef
Coral reefs are biodiverse ecosystems that can only develop where conditions are suitable for hard corals, as their skeletons form the rocky structure of the reef. Hard corals contain mutualistic zooxanthellae which need light for photosynthesis.
coral reef ecosystem
- Depth- water less than 50m, so enough light penetrates
- pH- above 7.8 so CaCO3 can be deposited in the skeleton
- Salinity- between 32 and 42 parts per thousand of dissolved ions to avoid osmotic problems
- Clarity- turbidity would prevent penetration of light so the water must be clear
- Temperature- 23-29 degrees Celsius so both the coral and zooxanthellae remain healthy
Terrestrial biome distribution
- With any combination of abiotic factors, one particular type of ecosystem is likely to develop
- For example, taiga (boreal forest) develops in subarctic regions, with spruces and other conifers as the dominant trees
- Species composition will vary depending on the geographical location, but the adaptations of the species are likely to be similar
- All ecosystems of a specific type are a biome
- Temperature and rainfall are the principal determinants of biome distribution on earth
- The most likely ecosystem with any particular combination of these factors can be shown using a graph
what are biomes?
Biomes are groups of ecosystems that resemble each other, even though they may be widely separated worldwide. The resemblance is due to similar abiotic conditions, with organisms evolving similar adaptations.
Climatic conditions in major biomes (temperate forest, grassland, taiga, tundra):
Temperate forest: temperatures moderate with summers warm and winters cold, rainfall medium to high, moderate light intensity
Grassland: temperatures medium to high in summer but may be cold in winter, rainfall moderate with a dry season, light intensity medium/high
Taiga (boreal forest): temperatures low with short summers, precipitation medium to high, light intensity low to medium
Tundra: temperatures very low with very short summer, precipitation low to medium (mostly as snow), low light intensity
Climatic conditions of hot deserts
Very high daytime temperatures and much colder nights. There is little rainfall and long droughts. Soil development is minimal, with little soil organic matter. The saguaro cactus and fennec fox are adapted to these conditions.
Adaptations of saguaro cactus (inhabitant of hot desert environment)
- wide-spreading roots to collect water from a wide range
- tap roots to collect water from deep in the subsoil
- wide stems with water storage tissue
- pleated stems that shrink in droughts and swell after rain
- vertical stems to avoid overheating by hot midday sun
- thick waxy cuticle on stem epidermis- less transpiration
- leaves. reduced to spines- less surface area so less transpiration
- CAM metabolism so stomata open only at night and close during the heat of the day, reducing transpiration
Adaptations of Fennec fox (inhabitant of hot desert environment)
- nocturnal so it avoids daytime temperatures
- builds underground den where it stays cool in the day
- long thick hair, heat insulation in cold nights and hot days
- hair covers the pads of the feet to provide insulation when walking on very hot sand
- pale-coloured coat reflects sunlight (a darker coat would absorb it)
- large ears radiate heat- keeps body temperature down
- ventilation rate rises very high (panting) to cause heat loss by evaporation
Conditions of tropical rainforest envronment
High light intensity, high temperatures, no cold season and much rainfall. Soils tend to be thin and nutrient-poor due to leaching. Yellow meranti and the spider monkey are adapted to these
Yellow meranti adaptations (TRF inhabitant)
- grows over 100m tall to avoid competition for light
- trunk of hard dense wood to provide support against wind stress
- trunk buttressed at base to provide support in shallow soil
- smooth trunk to shed rainwater rapidly
- oval leaves with pointed tips to shed rainwater rapidly
- evergreen leaves to carry out photosynthesis all year
- leaf enzymes work in temperatures as high as 35 degrees celsius
- flowers and seeds produced in large quantities only about one year in five, to deter animals that eat the seeds.
Spider monkey adaptations (TRF inhabitant)
- long arms and legs for climbing and reaching for fruit
- flexible shoulders allowing swinging from tree to tree
- large hook-like thumbless hands to grasp branches and lianas (woody vines) and pick fruit
- feet can grasp branches so arms can be used for feeding
- long tail to grip branches
- highly developed larynx for communication in the dense rainforest canopy
- only awake in the daytime- vision is better so movement between branches is safer
- breeding in any season, as food always available
What are ecological niches?
The position of a species within an ecosystem
A key concept in ecology is that each species in an ecosystem fulfils a unique roll, called its ecological niche. Niches have both biotic and abiotic elements.
- Zones of tolerance for abiotic variables determine the habitat of a species- where it lives in the ecosystem
- Food supply is a biotic element and an be autotropic (synthesis using an energy source, water and carbon dioxide), or heterotrophic (taking food from other organisms). To minimise competition, species become specialists in sourcing food. To compete effectively with any specialised mode of nutrition, adaptations are required.
- Other biotic elements of ecological niches are utilization of other species to provide a diverse range of services, such as pollination of flowers or nesting sites in tree holes.
The ecological niche of a species is made up of many factors- it is multidimensional. Unless all the dimensions of the niche are satisfied in an ecosystem, a species will not be able to survive, grow or reproduce.
what are requirements for obligate aerobes?
Oxygen must be continually available for aerobic respiration
what are requirements for obligate anaerobes?
Conditions must be anoxic as oxygen kills or inhibits the organism
what are requirements for facultative anaerobes
Oxygen is used if available but anoxic conditions are tolerated
what are examples of obligate aerobes?
- all plants and animals
- micrococcus luteus
what are examples of obligate anaerobes?
- clostridium tetani
- methanogenic archaea
what are examples of facultative anaerobes?
- E-coli
- Saccharomyces
what is photosynthesis?
In photosynthesis energy from sunlight is used for fixing carbon dioxide and making the carbon compounds such as sugars and amino acids on which life is based.
which organisms photosynthesise?
- plants- mosses, ferns, conifers and flowering plants
- eukaryotic algae- including seaweeds that grow on rocky shores and unicellular algae such as chlorella
- cyanobacteria- (blue-green bacteria) and several other groups of bacteria, but many aren’t photosynthetic
which domains of life does photosynthesis occur in?
Photosynthesis occurs in two of three domains of life (eukaryotes and bacteria). It does not occur in the other domain (archaea)
what is Holozoic nutrition?
Animals obtain supplies of carbohydrates, amino acids and other carbon compounds by consuming food. They are heterotrophic because the carbon compounds come from other organisms. Molecules such as polysaccharides and proteins must be digested before they can be absorbed. Digestion in most animals happens internally , after the food has been ingested. This is holozoic nutrition- whole pieces of food are swallowed and then fully digested.
what are the stages of holozoic nutrition?
- ingestion- taking the food into the gut
- digestion- breaking large food molecules into smaller molecules
- absorption- transport of digested food across the plasma membrane of epidermis cells and thus into the blood and tissues of the body
- assimilation- using digested foods to synthesise proteins and other macromolecules; this makes them part of the body’s tissues
- egestion- voiding undigested material from the end of the gut
why arent spiders holozoic?
Some animals digest their food externally and so aren’t holozoic. Spiders for example inject digestive enzymes into their prey and suck out the liquids produced. They absorb the products of digestion in their gut and assimilate them
what is mixtrophic nutrition?
Some protists (unicellular eukaryotes) can obtain carbon compounds from other organisms or can make them themselves. Organisms that aren’t exclusively autotrophic or heterotrophic are mixotrophic.
what are facultative mixotrophs?
Facultative mixotrophs can be entirely autotrophic, or use both modes. Euglena gracilis, for example has chloroplasts and carries out photosynthesis when there is sufficient light, but it can also feed on detritus or smaller organisms by endocytosis.
what are obligate mixotrophs?
Obligate mixotrophs cannot grow unless they utilise both autotrophic and heterotrophic modes of nutrition. This may be because the food that they consume supplies them with a carbon compound that they cannot synthesise. In other cases, a protist that does not have its own chloroplasts obtains them by consuming algae. It uses the “klepto-chloroplasts” obtained this way for photosynthesis until they degrade and have to be replaced.
what is saprotrophic nutrition?
Saprotrophs feed on dead organic matter, but have cell walls so cannot take it in by endocytosis. Instead, they secrete organic matter around them and digest it externally. They secrete proteases to digest proteins into amino acids and other enzymes depending on the composition of the dead organic matter , for example cellulase to digest cellulose into glucose.
If the small soluble products of digestion diffuse into the saprotrophs plasma membrane, they are absorbed and used. Many types of bacteria and fungi are saprotrophic.
what are Archaea?
There are three domains of life: archaea, bacteria and eukaryotes. The archaea are unicellular and have no nucleus, which is a similarity with bacteria. In other respects, archaea are closer to eukaryotes. Some types of archaea are adapted to extreme environments such as hot springs, salt lakes and soda lakes. Many are are difficult to culture in the laboratory, so they are less well researched than the other domains of life. Archaea are extremely diverse in their sources of energy for ATP production and carbon.
3 main types of archaea; photoheterotrophs, chemoheterotrophs and chemoautotrophs
how do Chemoheterotrophs gain energy for ATP production?
Oxidation of carbon compounds obtained from other organisms
how do Chemoheterotrophs gain carbon compounds?
Obtained from other organisms- not photosynthesis
how do photoheterotrophs gain energy for ATP production?
Absorption of light using pigments (not chlorophyll in archaea)