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Biology A2 > A2 Biology Term 1 > Flashcards

A2 Biology Term 1 Flashcards

1
Q

Define the terms species, ecosystem and niche

A

Species: Group of organisms that resemble each other structurally and biochemically which can breed with each other to form fertile offspring.

Ecosystem: A unit made up of biotic and abiotic components interacting and functioning together in a given area.

Niche: the functional role or place of a species within an ecosystem. This includes its feeding interactions, habitat, lifecycle and location. This provides a description of the specific environmental features to which the species is adapted.

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2
Q

Define the terms habitat, population and community

A

Habitat: the locality in which an organism occurs

Population: All of the organisms of one particular species within a specified area at a particular time.

Community: All of the populations of all the species within a specified area at a particular time.

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3
Q

List the different ways in which biodiversity can be considered and define it

A
  • The total number of species known and their relative abundance.
  • variation in ecosystem or habitat
  • genetic variation within species
  • Biodiversity can hence be defined as the total number of species living in a defined area.
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4
Q

Why is it important to use a random sample when determining biodiversity?

A
  • A random sample is used so that a complete census will not have to be taken as taking a census is impractical due to the number of organisms in the area.
  • The sample must be random in order to ensure that every individual of the population has an equal chance of being selected.
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5
Q

Describe the different ways of assessing abundance and distribution of organisms

A

Quadrats: Square frames that are placed according to random numbers after area is divided into grid of numbered sampling squares.

Transect: Samples data at right angles to impact of unidirectional physical forces. Line or belt transect is used to see number of organisms present in a straight line.

Mark, release and recapture: First sample is caught for marking. Large samples should be captured. Marked individuals distribute randomly among population after release. After this, second sample is caught, some of which are marked.

Size of population = (first sample marked x recaptured)/ marked recaptured

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6
Q

Describe the difference between Spearman’s rank correlation and Pearson’s linear correlation

A

Spearman’s rank: for ordinal (non-normal) data - values or observations that can be ranked

Pearson’s linear: for normal data - quantitative data that cannot be ranked.

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7
Q

Describe the significance of diversity and state the formula for Simpson’s Index of Diversity

A
  • the diversity of species present in a habitat is also an indicator of the stability of the community.
D = 1 - (Σ(n/N)^2) 
n = number of individuals of each species
N = total number of organisms of all species found
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8
Q

Define taxonomy and describe the binomial system of naming

A

Taxonomy: Science of classification

- first part is genus, second part is species

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9
Q

List the hierarchical scheme of classification

A

Doman, Kingdom, Phylum, Class, Order, Family, Genus, Species

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10
Q

Describe the features of archaea, bacteria and eukarya

A

Archaea:

  • extremophile prokaryotes due to being found in hostile environments.
  • Have larger RNA molecules in ribosomes
  • have a circular genome
  • histones present, introns absent
  • cell wall not made of peptidoglycan
  • have an ether linkage and branched hydrocarbon tails in lipids of cell membrane.

Bacteria:

  • circular genome
  • histones and introns absent
  • Cell wall made of peptidoglycan

Eukaryota:

  • chromosomes
  • histones and introns present
  • cell wall sometimes present, never of peptidoglycan.
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11
Q

Describe the eukaryotic kingdoms

A

Protoctista:

  • unicellular or multicellular with no differentiated tissue
  • some have cell walls
  • some are heterotrophic some are autotrophic

Fungi:

  • multicellular except yeast. Not differentiated into tissues, non-motile.
  • Cell walls of chitin
  • Heterotrophic
  • made of branching, tube-like hyphae
  • reproduce by spores, produced asexually and sexually

Plantae:

  • multicellular, differentiated into tissues, non-motile
  • cell walls of cellulose
  • autotrophic
  • mosses have no true roots, no vascular tissue and have spores.
  • ferns reproduce by spores
  • flowering pants reproduce by seeds and have efficient vascular tissue.

Animalia:

  • Multicellular, differentiated into tissue, motile
  • cells sometimes have cilia or flagella
  • heterotrophic
  • no cell wall
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12
Q

Describe the viruses and state features of viruses

A
  • disease causing agents that are inactive outside a host cell.
  • within the host they are highly active genetic programmes that take over biochemical machinery.
  • Lysis of the host cell causes viruses to be released causing new infections.

Features:

  • not cellular structure, consists of nucleic acid surrounded by capsid
  • may be an additional external envelope of membrane made of lipids and proteins
  • Extremely small, 20-400 nm
  • reproduce inside specific living cells
  • have to be transported between hosts
  • highly specific
  • classified based on number of strands of nucleic acid and whether it is DNA or RNA
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13
Q

Discuss the reason for a decline in biodiversity and describe the threats of this on aquatic and terrestrial ecosystems

A
  • As the human population has grown exponentially, our activities have affected the biosphere causing changes. Such changes threaten the biodiversity of ecosystems.
  • Rainforests are being rapidly destroyed by deforestation meaning the great biodiversity of rainforests are threatened.
  • Corals reefs are dying as a result of coral mining and pollution of run-off water from agriculture. Rising sea temps, rising sea levels, and acidification of oceans due to rising levels of atmospheric CO2 are also threats.
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14
Q

Describe the reasons why biodiversity must be maintained

A
  • Genetic diversity and evolution: If diversity is low then gene pool is low and inbreeding is more likely to occur. This leads to homozygosity meaning the organism is unable to adapt to future changes in environment.
  • Reservoir for genes in agriculture: Genes found in wild species can be used for resistance against pests, disease and changing abiotic factors allowing survival of domesticated species.
  • Origin of new drugs: Many extracted from substances manufactured from plants.
  • Ecotourism: Responsible travel to natural areas which conserves environment and improves welfare of local people.
  • Climactic and scientific importance: Natural habitats are ‘outdoor laboratories’ where we learn about the evolution of life forms. Furthermore, autotrophic organisms are CO2 sinks which reduce climate change.
  • Ethical basis: Moral obligation to pass on to future generations the diversity we have inherited and enjoyed.
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15
Q

Discuss the ways in which endangered species can be protected?

A

Nature reserves:

  • Carefully selected areas that are set aside for restricted access and controlled use to allow maintenance of biodiversity.
  • Should have continuous monitoring, maintenance of boundaries to limit harmful human interference, ensuring of lifecycle completion, and restocking and reintroductions of common species.

Zoological gardens:

  • Captive breeding programmes allow animals to be shipped between zoos and bred to ensure gene pool of species are maintained.
  • Artificial insemination or in-vitro fertilisation may be used.
  • However, reproduction of species may make them vulnerable. Cost is also high.

Seed banks:

  • Exploitation of seeds dormancy so that seeds can be stored and a large gene pool can be maintained in a small area.
  • For such dormancy, dry and cold conditions are required.
  • Samples are regularly germinated to replenish the seed stores.
  • Seeds with limited longevity are grown in botanic gardens.
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16
Q

State the method of assisted reproduction

A
  1. Menstrual cycle is blocked as pituitary gland is suppressed by injection of hormone
  2. Synthetic FSH is injected so that superovulation occurs (many eggs are released)
  3. Sperm taken from males or from frozen sperm stocks
  4. Several eggs are removed from the ovaries positioned with the aid of ultrasound
  5. Eggs are mixed with sperm. Microscopic examination used to check for fertilisation.
  6. Zygotes incubated at body temp for 2-3 days
  7. Microscopic examination to confirm embryos have reached 4-8 cell stage
  8. Several embryos are transferred into uterus in expectation that some will implant.
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17
Q

Define alien species and describe what makes it an invasive species

A

Alien Species: Introduced plants or animals that have been accidentally or deliberately transferred from their habitats to a new environment with suitable abiotic factors.

Invasive Species: If an alien species takes over local ecosystems in an aggressive way and so is detrimental to the food chain, leading to the decline of native species.

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18
Q

Describe the different ways in which culling and control has become necessary and how it has been implemented

A

Grey Squirrels:

  • Causes the decline of the native red squirrel species.
  • Also damages young trees
  • Maize seeds with a high dose of oestrogenic chemicals is introduced into woodland during breeding season.
  • Fertility of squirrels are thus compromised. This is culling by contraception.

Rabbit:

  • Destroys grassland used in agriculture
  • myxoma virus which causes myxamatosis in rabbits was introduced.
  • This kills of a large proportion of the rabbits who lacked immunity.
  • This means that the rabbits evolved to live in balance with other organisms of the community.

Japanese knotweed:

  • Lack the usual limiting factors found in Japan meaning plants grow dense, submerged thickets that overshadow native water plants.
  • Plant also has chemical in leaves which discourage predation from local organisms. In Japan, predators have evolved to cope with this chemical.
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19
Q

Discuss the role of NGO’s in conservation

A

WWF:

  • to build a future in which humans live in harmony with nature
  • they work to conserve nature and to protect nature against threats to biodiversity.

CITES:
- ensures international trade of animals does not threaten survival of any species.
- classifies organisms based on threatened level:
1. Species in danger of extinction: trade is prohibited
2. Species that are affected by trade: Permit required
3. Species protected in one country that is a CITES
member and has petitioned others for help in
controlling international trade of species.

20
Q

Define bioremediation

A

The process of exploiting microorganisms in the removal of pollutants from the environment

21
Q

Describe the different ways in which bioremediation is used

A

Environment:

  • removal of engine oil that accumulate on surfaces that are degraded by chemoheterotrophic bacteria if kept moist by rain.
  • removal of oil slicks from tanker spills can be speede by spraying the oil with inorganic nutrients such as phosphates and nitrates which aid sapotrophic bacteria and speed up bacteriological oxidation.

Soils:

  • pesticides that remain in the soil can be degraded using microorganisms
  • Bacteria can also be used to break down industrial solvents
  • the leaching of chemicals into water causes pollution which can be degraded by microorganisms.
  • The number of microorganisms can be enhanced by drilling of wells and vents so that micronutrients and oxygen reach the microorganisms.
22
Q

List processes which require energy

A
  • reactions of metabolism: formation of complex molecules e.g. protein synthesis. This is known as anabolism
  • active transport of particles across membranes
  • movement: both due to muscle contractions and of cell organelles
  • formation and secretion of substances from cells
  • cell division and formation of organelles
23
Q

Describe ATP and explain what makes it suitable as energy currency

A

Adenosine Triphosphate:

  • it is the source of energy for chemical changes in the body
  • energy is released when ADP and Pi is formed from ATP
  • in respiration ATP forms from ADP and Pi
  • it is a small, soluble organic molecule meaning it can be moved easily within cells and organisms by facilitated diffusion.
24
Q

Describe the roles of coenzymes in respiration

A

NAD: Accepts hydrogen ions and electrons and is reduced. These hydrogen ions can be passed on for transport of these ions.

FAD: Similar hydrogen-carrying molecule

Coenzyme A: Involved in removal of two-carbon fragments from certain carbohydrates and lipids during respiration.

25
Q

Describe the ways in which ATP is generated

A
  1. Substrate-Level phosphorylation:
    - takes place in cytosol
    - part of glycolysis and Kreb’s cycle
    - Amount of ATP is trivial
  2. Associated with electron transport chain:
    - takes place in mitochondria
    - bulk of ATP formed this way
26
Q

Describe and explain the relative energy values of different molecules

A
  • Lipids transfer the most energy
  • This is because lipids contain the most hydrogen
  • This is because most energy comes from the oxidation of reduced NAD and the resultant formation of water
27
Q

Define respiratory quotient

A

The ratio of the amount of CO2 produced to the amount of oxygen taken in

28
Q

State the stages of aerobic respiration

A
  1. glycolysis
  2. link reaction
  3. Krebs cycle
  4. electron transport chain and oxidative phosphorylation
29
Q

Describe the process of glycolysis

A
  1. Glucose is activated by reactions with ATP for phosphorylation. Product 1,6 bisphosphate
  2. Lysis forming two triose phosphate molecules
  3. Oxidation occurs by removal of hydrogen using NAD to form reduced NAD. The enzyme is dehydrogenase.
  4. ATP synthesis occurs as an inorganic phosphates are added to each triose phosphate and they are then removed to form ATP from ADP. The resulting molecules are two pyruvate molecules.
30
Q

Describe the link reaction

A
  • Link reaction only occurs when oxygen is available
    1. Pyruvate is actively transported from the cytosol into the matrix of the mitochondrion.
  1. Carbon dioxide is removed from the pyruvate. This is called decarboxylation
  2. At the same time, oxidation occurs by removal of hydrogen using NAD. This is dehydrogenation. The product of these reactions is an acetyl group.
  3. This acetyl group is combined with coenzyme A forming acetyl coenzyme A.
31
Q

Outline the Krebs cycle

A
  1. Acetyl coenzyme A reacts with oxaloacetate to form citrate and coenzyme A which is reused.
  2. Citrate undergoes decarboxylation followed by oxidation using NAD to form a 5-carbon acid.
  3. ATP is formed at the substrate level. Decarboxylation occurs. Oxidation occurs three times - NAD, FAD and finally NAD. Reforms oxaloacetate
    - This cycle occurs twice for one molecule of glucose as there are two pyruvate molecules.
32
Q

Outline the process of oxidative phosphorylation

A
  • reduced NAD is oxidised to reform NAD
  • this releases high energy electrons and H+ ions
  • electrons are passed between carriers in the mitochondria releasing their energy to form ATP
  • the hydrogen ions, electrons and oxygen combine to form water.
33
Q

Explain how the energy transfer for ATP synthesis is brought about

A
  • inner membrane of mitochondria is a barrier to movement of ions and electrons
  • Protons hence have to be pumped across using energy
  • Carrier proteins are provided with this energy by the energy of oxidation through the energetic electrons so can pump H+ into the inter-membrane space. This causes the pH to drop.
  • A gradient in H+ concentration builds up across inner membrane and generates a potential difference. Represents a store of potential energy.
  • Protons flow back into the matrix by facilitated diffusion through ATP synthase molecules. Energy is hence transferred to the synthesis of ATP from ADP and Pi.
  • The reaction is catalysed using ATP synthase
34
Q

Describe the relationship between different structures in the mitochondria and its function

A

External double membrane: permeable to pyruvate, CO2, O2, NAD and reduced NAD

Matrix: site of link reaction and Krebs cycle

Inner Membrane:

  • Surface area increased by cristae increasing opportunities for ATP synthesis
  • impermeable to H+ allowing formation of potential difference between matrix and inter-membrane space.

Inter-membrane Space: Tiny space - allows accumulation of protons which generates a large p.d. This allows phosphorylation of ADP to occur.

35
Q

Describe the different pathways for anaerobic respiration

A
  • Without oxygen the link reaction cannot occur. Eventually, tissue without oxidised NAD means the glycolysis will cease.

Alcoholic Fermentation:

  • pyruvate undergoes decarboxylation to form ethanal
  • reduced NAD is oxidised to NAD. Alcohol dehydrogenase catalyses this reaction. Ethanal is the hydrogen acceptor and forms ethanol.

Lactic Acid Fermentation:
- reduced NAD is similarly oxidised to NAD but lactate dehydrogenase is used instead. Pyruvate is the hydrogen acceptor and lactic acid is formed.

36
Q

Explain why the yield of ATP is less in anaerobic respiration

A
  • yield is much smaller per unit of glucose molecule respired
  • this is because no oxidative phosphorylation occurs and only substrate level phosphorylation occurs.
  • most ATP in aerobic respiration comes from oxidative phosphorylation
37
Q

Explain the term oxygen debt

A
  • During strenuous exercise lactic acid builds up in muscles due to anaerobic respiration.
  • Lactic acid is converted back to glucose in the liver and is transported in the blood stream. This requires energy from respiration and so requires oxygen for respiration.
  • this oxygen is called the ‘oxygen debt’
38
Q

Describe the adaptations of rice to its waterlogged conditions

A
  • Grows in waterlogged soil meaning there is no oxygen available for the roots
  • ground tissue cells (parenchyma) have huge, interconnecting air spaces between them, particularly in the roots. This is known as aerenchyma tissue.
  • Such tissue aids the diffusion of oxygen to the roots allowing normal growth and metabolism of the roots.
  • Enzymes such as ethanol dehydrogenase metabolise ethanol produced during alcoholic fermentation.
  • Root cells also have higher tolerance for ethanol than other cereals.
39
Q

Explain why organisms become extinct

A

Climate change:

  • causes increased water temperature, increased CO2 results in ocean acidification.
  • causes mass bleaching and death of corals in coral reefs

Competition:
- Organisms are in same niche leading to exclusion of one

Habitat loss:

  • Habitats provide the environment required for survival
  • destruction of rainforests kill many organisms and greatly harms biodiversity.

Destruction by humans:

  • animals are hunted for resources such as hide, ivory and meat.
  • their eggs may have also been taken preventing reproduction
  • as animals encroach on human settlements they are hunted and killed
40
Q

Describe photosynthesis

A
  • It is a process in which green plants use the energy of sunlight to produce complex organic molecules, mainly sugars.
  • Light is trapped by chlorophyll pigments, present in chloroplasts and used for photosynthesis
  • It is a redox reaction
41
Q

Describe the different pigments used in photosynthesis

A
  • Chlorophyll a: Rf value of 0.65
  • Chlorophyll b: Rf value of 0.45
  • Carotenoids: Accessory pigments which pass the light energy they absorb to chlorophyll. e.g. carotene, xanthophyll: responsible for different colours
42
Q

Describe the absorption and action spectra of chlorophyll

A

Absorption spectrum: Obtained by measuring the absorption of different coloured lights to show the amount of light absorbed over the wavelength range of visible light. Red and blue is best.

Action spectrum: Wavelengths of light that bring about photosynthesis.

43
Q

What is a photosystem?

A

A structure that is made up of a group of chlorophyll molecules and other accessory pigments. Photosystems are found in the thylakoid membrane. All of the pigment molecules harvest light energy and funnel the energy into a single chlorophyll molecule known as the reaction centre.

PSI absorbs light of wavelength 700nm

PSII absorbs light of wavelength 680 nm

44
Q

Describe the light dependent stage of photosynthesis and describe what happens with the products formed

A

1- light energy reaches PSII activating a pair of ground-state electrons, raising them to an excited state.

2- These electrons have come from the photolysis of water which also forms oxygen and protons.

3- The electons are captured by an electron acceptor and then move down an ETC.

4- As the electrons move down the ETC, their energy level falls back down to ground state and the energy is used to pump protons from stroma into thylakoid space forming a proton gradient across the membrane.

5- The electrons enter PSI and are again excited by light energy, moving through another ETC and their energy is used to form reduced NADP in the stroma.

6- Protons move back down concentration gradient back to stroma through ATP synthase enzyme causing synthesis of ATP. This is non-cyclic photophosphorylation.

7- The reduced NADP and the ATP are used in the light-independent reaction.

45
Q

Describe the Calvin cycle

A
  • This is the light-independent stage and occurs in the stroma
    1. CO2 diffuses into chloroplast and is combined with acceptor molecule, RuBP, a 5-carbon sugar. An enzyme, rubisco, is present. This is known as fixation .The product of this reaction is two molecules of 3-carbon sugar glycerate-3-phosphate or GP. It is an organic acid.
    2. GP is reduced to triose phophate. Both reduced NADP and ATP are required for this reduction to occur.
    3. For every 6 molecules of triose phosphate, 5 are use to form 3 molecules of RuBP. The other molecule is used in the synthesis of other compounds. This requires ions as well as energy from ATP.
46
Q

Describe cyclic photophosphorylation

A
  • If CO2 concentration is low then fixation will cease and NADP disappears.
  • This means non-cylic photophosphorylation can no longer occur.
  • Instead, excited electrons from PSI fall back to where they came from through the ETC allowing the pumping of protons to continue.
  • This means that ATP formation continues.

Biology A2 (3 decks)

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