Biology - Prelim Study

Question 1

What size are cells?

Answer 1

All shapes and sizes - ranging from millimetres to microns

Question 2

What size is a typical plant cell?

Answer 2

Typical plant cell 20-100 μm

Question 3

What size is a typical animal cell?

Answer 3

Typical animal cell 5-20 μm

Question 4

What size is a bacterial cell?

Answer 4

Bacterial cell 0.1-5 μm

Question 5

What is an organelle?

Answer 5

An organelle is a tiny cellular structure that performs specific functions within a cell

Question 6

What are the two main types of cells?

Answer 6

1. prokaryotic
2. eukaryotic

Question 7

What is a prokaryotic cell?

Answer 7

Prokaryotic cells are single-celled organisms with no membrane bound organelles. Eg no nucleus.

They have a capsule, cell wall, cell membrane, cytoplasm, nucleoid, ribosomes, plasmids, pilus and flagella.

The size of a cell ranges from 1-10microns

Examples include - Monera (bacteria) and Archaea

Question 8

What is a Eukaryotic cell?

Answer 8

Eukaryotes have a membrane bound nucleus with many cell organelles to perform several cellular functions within the system

Eukaryotic cells are more complex than prokaryotic cells

They are larger at the cell cell ranges from 10-100 microns

Examples include - Animals, Muscle cell, plants, fungi, yeast cells and protists

Question 9

What is the nucleus?

Answer 9

The nucleus is the control centre of the cell and coordinates all of the cell’s activities

It contains the DNA in chromosomes

It is surrounded by a double membrane

The nuclear pore allows movement into and out of the cell

Question 10

What is the nucleolus?

Answer 10

RNA is made here (RNA is used to make proteins)

The nucleolus is located in the nucleus.

Question 11

What is the mitochondria?

Answer 11

The mitochondria generate most of the cells supply of chemical energy called ATP

This is created by respiration

They have a highly folded double membrane. This increases the surface area so more respiration can take place

Question 12

What is the chloroplast?

Answer 12

Chloroplast contains chlorophyll needed to carry out photosynthesis (where light is absorbed and carbon dioxide and water are converted into glucose and oxygen)

Chloroplast have a double membrane and the internal membranes are in stacks called grana

Chloroplasts trap light energy, which is used to split water molecules into hydrogen and oxygen in the process of photosynthesis

The hydrogen then combines with carbon dioxide to make glucose, and the oxygen is released into the atmosphere as a waste product

Is not in animal cells

Question 13

What are vacuoles?

Answer 13

Vacuoles are fluid filled storage spaces for water, salts, sugars, amino acids and other chemicals

They have a single membrane

Plant vacuoles provide structural support by helping to maintain turgor

Question 14

What is the Endoplasmic reticulum?

Answer 14

Rough E.R is abundant in cells that actively produce and export proteins, such as pancreatic cells, which secrete digestive enzymes

Smooth E.R contains the enzymes involved in the synthesis of molecules other than proteins, such as phospholipids and steroids

Question 15

What is the Golgi apparatus?

Answer 15

They receive, sort, store and secrete materials

Golgi bodies are membrane stacks with transport vesicles at the perimeter

The vesicles transport the proteins from one cisternae to the next, where they are modified for use by the cell, or the transport out of the cell

Question 16

What are lysosomes?

Answer 16

Lysosomes are round and have a single membrane

They are vesicles that store enzymes to break down old organelles and some molecules

They are more common in animal cells

Question 17

What are ribosomes?

Answer 17

Ribosomes are tiny round structures that are responsible for helping the making of proteins

They do not have a membrane and are often attached to the endoplasmic reticulum

There can be millions of them

Question 18

What is the cell wall?

Answer 18

The cell wall is a rigid structure that surrounds the cell membrane of plant cells, fungal cells and some prokaryote cells. It is not in an animal cell.

In plants, the cell wall is composed mainly of cellulose. Fungal cell walls are made of chitin

The cell wall provides support, prevents expansion of the cell, and allows water and dissolved substances to pass freely through it

Lignin in the cell walls of the woody plants, especially the xylem, gives them additional strength

Question 19

What is the cell membrane?

Answer 19

The cell membrane provides protection for a cell.

It provides fixed environments inside the cell and that membrane has several different functions

One is to transport nutrients into the cell and also to transport toxic substances out of the cell

Question 20

What is the surface area of a cell?

Answer 20

The surface area of the cell is the outside area of the cell

Question 21

What is the volume of a cell?

Answer 21

The volume of a cell is the inside capacity or amount of space inside the cell

Question 22

What is the surface area to volume ratio?

Answer 22

The surface-area-to-volume ratio or SA:V, is the amount of surface area of an organism divided by its volume.

Organisms must take in food, oxygen and water, and other essential substances, from the environment. Plants also need carbon dioxide for photosynthesis. Organisms also need to remove waste substances. Small organisms exchange these essential and waste substances between themselves and the environment. They do this over their body surface. Simple chemical substances can
diffuse in and out of their bodies.
Inside their bodies, in small organisms, substances don’t have to move far.
The size of their surface, or surface area, defines how quickly they can absorb substances. The size of their volume defines how much of these substances they need.

As the cell size increases the surface area to volume ratio decreases.

Question 23

What are the factors affecting the rate of diffusion across a cell membrane?

Answer 23

1. Membrane thickness:
   For nutrients to diffuse into a cell they must cross the cell membrane. Cell membranes are extremely thin to allow for the diffusion of materials across the cell membrane
2. Concentration gradient:
   The greater the concentration gradient (the difference in the concentration either side of the membrane) the greater the rate of diffusion
3. Surface Area to volume ratio:
   The larger the area over which diffusion can occur, the greater the rate of diffusion
4. Temperature and pressure
   As with any chemical reaction, increasing the temperature or pressure increases the kinetic energy of the particles, thus increasing the rate of diffusion
5. Types of Molecules
   - Lipid soluble (non polar) such as alcohol dissolves in the lipid bilayer
   - Water soluble molecules tend to be repelled however small molecules such as water are small enough to pass between phospholipids
   - Uncharged molecules such as oxygen and carbon dioxide pass between phospholipids
   - Large water soluble molecules (polar) such as sugars and amino acids cannot pass directly across unless through protein channels
   - Ions cross cellular membranes is mediated by transport proteins and an input of energy

Question 24

What are enzymes?

Answer 24

Enzymes are organic catalysts.

They are proteins made up of amino acids linked and folded to produce a three dimensional protein structure.

Enzymes are highly effective - only minute amounts are needed to bring about reactions and they can be reused

A substrate is the reactant on which an enzyme works

The enzyme fits with its substrate molecule at a precise place on its surface - the active site

The active site is a restricted region of the enzyme that binds and attaches to the substrate with weak chemical bonds

The shape of this site must not be altered if the enzyme is to function

Question 25

What is a catalyst?

Answer 25

A catalyst is a substance that speeds up or brings about a chemical change without being used up or changed in the reaction

Question 26

What are the models of the fluid mosaic model of the cell membrane?

Answer 26

1. Lock and key model
2. Induced fit model

Question 27

What is the lock and key model?

Answer 27

The shape of the enzyme permits it to bind at a particular site (called the active site) to the substrate molecule (reactant)

This causes a reaction to occur

The key (substrate) fitting the lock (enzyme)

Substrate + enzyme → enzyme/substrate complex → products + enzyme

Question 28

What is the induced fit model?

Answer 28

In some cases the shape of the active site of the enzyme varies slightly from that of the substrate and the two fit only after contact when the active site slightly changes it shape to accommodate the substrate perfectly

Question 29

What are the effects of the environment on enzyme activity?

Answer 29

pH
Enzymes are affected by changes in pH
The most favourable pH value is where the enzyme is most active
It is known as the optimum pH
Changes in pH may not only affect the shape of an enzyme but it may also change the shape or charge properties of the substrate so that either the substrate cannot bind to the active site or it cannot undergo catalysis
Within a narrow pH range, changes in the structural shapes of the enzymes and substrates may be reversible
But for a significant change in pH levels, the enzyme and the substrate may undergo denaturation
The optimum pH varies from one enzyme to another

Temperature
Enzymes are affected by temperature
If you heat them they can become permanently changed called denatured
They remain inactive even when temperature cools
Enzymes are inactivated at low temperatures
They can become active again when the temperature is returned to normal
Different enzymes have different temperature optimums
Enzyme activity increases to a certain point due to increase in kinetic energy of particles
Above or below the optimum temperature the efficiency (rate of reaction) decreases

Question 30

What is substrate concentration?

Answer 30

Adding more substrate to an enzyme solution will initially increase the rate of the reaction if active sites are available

However, there is a saturation point

Once all active sites are occupied further increase in substrate does not increase the rate of reaction

The higher the substrate concentration, the greater the rate of enzyme reaction, until all available enzymes are being used to catalyse reactions - saturation point

Question 31

Summarise substrate concentration?

Answer 31

Increasing substrate concentration will increase the activity of a corresponding enzyme

More substrates mean there is an increased chance of enzyme and substrate colliding and reacting within a given period

After a certain point, the rate of activity will cease to rise regardless of any further increases in substrate levels

This is because the environment is saturated with substrate and all enzymes are bound and reacting (Vmax)

Question 32

What is enzyme concentration?

Answer 32

If the amount of enzyme is increased the amount of product made per unit time increases

The total product does not increase

Question 33

What is the structure of a cell membrane called and what is it made up of?

Answer 33

The structure of the membrane is called a fluid mosaic model

It has a double layer made up of proteins and lipids called phospholipids

Question 34

What is a glycoprotein?

Answer 34

A glycoprotein is a molecule composed of a protein and a carbohydrate on the outside of the membrane

Question 35

What does the fluid mosaic model of the membrane show?

Answer 35

The fluid mosaic model of the membrane shows that membranes are not rigid structures instead they are fluid and able to drift along the plane of the membrane

Question 36

What is the function of a cell membrane?

Answer 36

Cell membranes are semi permeable.

This means they only allow some substances to move through bu not others

They have 3 functions:
1. They keep toxic substances out of the cell
2. They contain receptors and channels that allow specific molecules, such as ions, nutrients, wastes, and metabolic products to pass between organelles inside cell and the outside environment
3. They separate vital but incompatible metabolic processes conducted within organelles

Question 37

What do models do for biological concepts?

Answer 37

They enable processes to be observed and investigated easier
- Time factors (such as evolution)
- Size factors (molecular level)
- Simplifies complex processes

Question 38

What are some problems associated with modelling biological concepts? (List 4)

Answer 38

1. The fact that a model may oversimplify processes resulting in misconceptions
2. The relative time or size may be misrepresented
3. Most models can’t incorporate all the details of complex natural phenomena (incorporating these additional details would make the model too complex)
4. Models include some approximations as a convenient way to describe something that happens in nature (these approximations are not exact, so predictions based on them tend to be a little bit different from what you actually observe)

Question 39

What is the fluid mosaic model?

Answer 39

Many years of research have gone into attempting to accurately describe the structure of cell membranes

Our current accepted understanding is based on a model called the fluid mosaic model of cell membranes

Model proposed by J. Singer and G. Nicholson in 1972

Question 40

What is the evidence supporting the fluid mosaic model?

Answer 40

The behaviour of membranes, for example how they reseal themselves when punctured with a fine needle, led to the idea that they are not rigid, but more like a fluid

The membrane allows lipid soluble substances to pass through easily, suggesting a lipid basis

Question 41

What are unicellular organisms?

Answer 41

A unicellular organism has just one cell

Question 42

What are multicellular organisms?

Answer 42

Multicellular organisms - a multicellular organism has more than one cell and act like a community working together to ensure the organism survives and reproduces (eg. plants and animals).

Question 43

What is ingestion?

Answer 43

Ingestion - taking food into body

Question 44

What is digestion?

Answer 44

Digestion - breaking down food

Question 45

What is absorption in cells?

Answer 45

Absorption - moving food into cells

Question 46

What is assimilation in cells?

Answer 46

Assimilation - making food part of cell

Question 47

What is elimination in cells?

Answer 47

Elimination - removing unused food

Question 48

How can food be digested? (List 2)

Answer 48

1. Physical digestion
2. Chemical digestion

Question 49

What is physical digestion?

Answer 49

In physical digestion, food is broken down into smaller fragments via the acts of chewing (mouth), churning (stomach) and segmentation (small intestine)

Chewing (mouth)
Food is initially broken down in the mouth by the grinding action of teeth - called mastication
The tongue pushes the food towards the back of the throat, where it travels down the oesophagus as a bolus

Churning (stomach)
The stomach lining contains muscles which physically squeeze and mix the food with strong digestive juices (‘churning’)
Food is digested within the stomach for several hours and is turned into a creamy paste called chyme
Eventually the chyme enters the small intestine (duodenum) where absorption will occur

Question 50

What is peristalsis?

Answer 50

Peristalsis is the principal mechanism of movement in the oesophagus, although it also occurs in both the stomach and gut

Continuous segments of longitudinal smooth muscle rhythmically contract and relax

Question 51

What is segmentation?

Answer 51

Segmentation involves the contraction and relaxation of non-adjacent segments of circular smooth muscle in the intestines and helps to physically digest food

Segmentation contractions move chyme in both directions, allowing for a greater mixing of food with digestive juices

Question 52

What is chemical digestion?

Answer 52

Food is broken down by the action

Enzymes
- Enzymes are biological catalysts which speed up the rate of a chemical reaction (i.e. digestion) by lowering activation energy
- Enzymes allow digestive processes to therefore occur at body temperatures and at sufficient speeds for survival requirements
- Enzymes are specific for a substrate and so can allow digestion of certain molecules to occur independently in distinct locations

Question 53

What is amylase?

Answer 53

The digestion of starch is initiated by salivary amylase in the mouth and continued by pancreatic amylase in the intestines

Starch digestion by amylase does not occur in the stomach as the pH is unsuitable for amylase activity (optimal pH - 7)

Question 54

What are proteases?

Answer 54

The family of enzymes that can catalyst the digestion of proteins are called proteases

Pepsin is one such protease and acts in the stomach it has an optimum pH of 1.5-2

Another protease enzyme Trypsin is made in the pancreas and enters the duodenum

Question 55

What is bile?

Answer 55

The liver produces a fluid called bile which is stored and concentrated within the gallbladder prior to release into the intestine

Bile contains bile salts which interact with fat globules and divide them into smaller droplets (emulsification)

The emulsification of fats increases the total surface area available for enzyme activity (lipase)

Question 56

What are stomach acids?

Answer 56

The stomach contains gastric glands which release digestive acids to create a low pH environment pH ~ 2)

The digestive fluid formed in the stomach and is composed of hydrochloric acid (HCI), potassium chloride (KCI) and sodium chloride (NaCl)

The acidic environment functions to denature proteins, aiding the overall digestion

Question 57

What happens during absorption of nutrients, minerals and water?

Answer 57

During absorption, digested food monomers must pass from the lumen into the epithelial lining of the small intestine

The inner epithelial lining of the small intestine is highly folded into finger-like projections called villi (singular: villus)

Many villi will protrude into the intestinal lumen, greatly increasing the available surface area for material absorption

Once products are absorbed, they are then transported to the liver by means of the hepatic portal vein

Question 58

What is diffusion?

Answer 58

Diffusion is the movement of molecules in a fluid from areas of high concentration to areas of low concentration

Question 59

What is osmosis?

Answer 59

Osmosis is the passage of water molecules across a semipermeable membrane from a solution with a high concentration to a solution with a lower concentration

Question 60

What is elimination of solid waste?

Answer 60

The final step is the elimination of undigested food content and waste products

After food passes through the small intestine, the undigested food material enters the colon, where most of the water is reabsorbed

The semi-solid waste is moved through the colon by peristaltic movements of the muscle and is stored in the rectum

As the rectum expands in response to storage of faecal matter, it triggers the neural signals required to set up he urge to eliminate

The solid waste is eliminated through the anus using peristaltic

Question 61

What is the large intestine made up of?

Answer 61

colon and rectum

Question 62

What is the vascular system of a plant composed of?

Answer 62

Two vessels - the xylem and the phloem

Question 63

What is the xylem responsible for?

Answer 63

The xylem is responsible for transporting water

Question 64

What is the phloem responsible for?

Answer 64

The phloem is responsible for transporting sugar and other dissolved nutrients.

Question 65

Where do the xylem and phloem go?

Answer 65

They run throughout the whole plant, from the roots to the leaves.

Question 66

What is the circulatory system responsible for in mammals?

Answer 66

The circulatory system is the organ system in mammals that is responsible for the circulation of blood around the body.

It is essential for the transportation of nutrients, gases, hormones and blood cells to tissues around the body.

The main organs of the circulatory system are the heart, lungs, arteries, veins, capilliaries.

Mammals have a double cycle circulatory system.

The system of structures in vertebrates consisting of the heart, blood vessels, and lymphatics, by which blood and lymph are circulated throughout the body.

Question 67

What makes up an ecosystem?

Answer 67

Ecosystem is made up of organisms (biotic) living in an area that interact with each other and with the non-living (abiotic) environment in which they live.

Question 68

What makes up an environment?

Answer 68

Environment is made up of non-living factors.

Question 69

What are the steps of evolution?

Answer 69

1. Variation of a population due to natural mutation
2. Selection pressure is applied (ie. Physical changes, competition for resources)
3. The fittest survive
   4.Surviving organisms reproduce

Question 70

What is selection pressure in evolution?

Answer 70

Selection pressure are external agents which affect an organism’s ability to survive in a given environment.

They can be negative (decreases the occurrence of a trait) or positive (increases the proportion of a trait).

Question 71

List the 3 types of selection pressures in evolution.

Answer 71

1. Resource availability – Presence of sufficient food, habitat (shelter / territory) and mates.
2. Environmental conditions – Temperature, rainfall.
3. Biological factors – Predators and pathogens (diseases)

Question 72

How does population affect selection pressures?

Answer 72

Selection pressures can be:

1. density-dependent (affected by population size)
   or
2. density-independent (unaffected by population).

Question 73

What are the density dependent factors that may lead to changes in a population of organisms? (Remember - PANDA)

Answer 73

Predators
Availability of resources (eg. shelter, water)
Nutrient supply (ie. food source)
Disease/pathogenic spread
Accumulation of wastes

Question 74

What are the density independent factors that may lead to changes in a population of organisms? (Remember - PAW)

Answer 74

Phenomena (eg. natural disasters)
Abiotic factors (eg. temperature, CO2 levels)
Weather conditions (eg. floods, storms etc)

Question 75

What biotic factors may lead to changes in a population of organisms? (List 4)

Answer 75

• Living organisms within the same ecosystem
• Competition for resources (eg. food, territory)
• Predation
• Disease

Question 76

What abiotic factors may lead to changes in a population of organisms? (List 4)

Answer 76

• Climate (eg. temperature, wind)
• Shelter
• Availability of food and energy sources (eg. access to water, light, essential nutrients)
• Pollutants
• Chemicals (eg. pesticides and insecticides)

Question 77

List the 3 adaptations (or characteristics) that an organism can inherit and that makes it better suited to survive in its environment?

Answer 77

Structural Adaptations: refers to how an organism is built or structured so that it can survive in its natural environment.

Physiological Adaptations: are those that relate to how an organism functions and increase its chance of survival in its natural environment.

Behavioural Adaptations: refer to those actions performed or activity by an organism in response to a stimulus that improves its chance of survival.

Question 78

What is evolution by natural selection?

Answer 78

The theory of evolution suggests that all living organisms come from a common ancestor, which evolved into many different organisms over billions of years. Natural selection helps make that happen.

Question 79

What is genetic diversity?

Answer 79

Genetic diversity refers to the total number of genetic characteristics in the genetic make-up of a species.

Those organisms with characteristics that are selected for will survive and go on to reproduce. Speciation occurs if two populations become so different that they can no longer interbreed.

Question 80

What is micro evolutionary change?

Answer 80

Micro evolutionary change involves small scale changes within a population over shorter periods which is a group of organisms that share the same gene pool and can interbreed. Generally does not form new species

Question 81

What is macro evolutionary change?

Answer 81

Macro evolutionary change refers to the evolution of groups larger than species over millions of years. Thisis what we observe when looking at the history of life on Earth or the evolution of mammals.

Question 82

What is divergent evolution?

Answer 82

is where closely related species have similarities as a result of their relatively divergence from a common ancestor.

Natural selection accounts for their differences as they moved into different habitats and exposed to new selective pressures which would result on their evolution to be different.

eg. Wooly mammoth (extinct) and Modern elephant has a common ancestor

Question 83

What is convergent evolution?

Answer 83

is where more distantly related species show similarities, this could be as a result of having moved into similar environments.

They would have been exposed to similar selective pressures and so natural selection account for them evolving to become similar.

eg. shark (fish), ichthyosaur (reptile) and dolphin (mammal)

Question 84

What are punctuated equilibrium and gradualism (or gradual process of natural selection)?

Answer 84

Punctuated equilibrium and gradualism are two types of evolution that can occur in a species. A species can exhibit one or both of these evolutionary patterns.

Question 85

What is gradualism?

Answer 85

suggests that populations slowly diverge by accumulating changes in characteristics due to different selection pressures.

In this view, speciation is seen as a smooth and continuous process.

Question 86

What is punctuated equilibrium?

Answer 86

suggests that evolution occurs in short bursts of rapid change, followed by long periods of stability within populations.

Question 87

What is biochemistry?

Answer 87

Biochemistry is the study of chemicals found in cells.

Question 88

What is biochemical evidence?

Answer 88

Biological evidence for evolution involves determining sequences of chemicals such as amino acids in proteins, or the sequence of base pairs in DNA and then comparing them in organisms that may share an evolutionary relationship. The more closely related the organisms are (the more recently they separated from a common
ancestor), the more similar their biochemistry.

Question 89

What is amino acid sequencing?

Answer 89

Comparison of the sequence of amino acids within a protein common to two or more species.

Proteins include cytochrome C involved in respiration in plants and animals, Haemoglobin a protein found inanimals.

Question 90

What is DNA sequencing?

Answer 90

Compares the genetic code of two species. A gene (section of DNA) is isolated from each organism to be compared and copied. Fluorescent dyes distinguish between the four bases in DNA, a computer prints out the bases.

Question 91

What is DNA –DNA Hybridisation?

Answer 91

Takes part of the DNA from a species, splitting the chains and seeing how well these recombine with DNA from another species.

If two strands from different species share similar sequences they will hybridise (come together to form a double strand).

The amount of heat then required to separate this hybrid molecule indicates how similar the two sequences are.

More heat indicates more hydrogen bonds formed, meaning more complementary base pairing due to similar sequences.

Less heat indicates fewer hydrogen bonds formed, meaning less base pairing has occurred because sequences are dissimilar.

Question 92

What is comparative anatomy?

Answer 92

Comparative anatomy – the study of similarities and differences in the structure (anatomy) of living organisms.

If organisms are more closely related, they should be more similar.

Organs that have the same basic plan to their structure, but show modifications because they are used indifferent ways are termed homologous structures—they have the same evolutionary origins.

Homologous structures (similar structures having a similar origin) do not necessarily have a similar function.

Example: in vertebrate (mammal) front limbs (pentadactyl limbs). The same skeletal structure has been adapted for grasping, walking, swimming or flying.

Therefore the wing of a bird, the forearm of a lizard and the flipper of a whale are homologous, because all share a common basic bone structure, suggesting that they shared a common evolutionary origin.

Question 93

What is comparative embryology?

Answer 93

Embryos of many different species are very similar in early stages of development.

In all terrestrial vertebrates, non-functional gill slits are seen in early embryos. Human embryos show a primitive tail.

We could explain these observations by assuming that vertebrates share a common ancestor as part of their evolutionary history. The gill slits suggest that this common ancestor of vertebrates lived in an aquatic environment.

Question 94

What is biogeography?

Answer 94

Biogeography is the study of the geographical distribution of organisms, both living and extinct.

The Darwin- Wallace theory of evolution proposes that, for a new species to arise, a group of individuals must become isolated (geographically separated) from the rest.

The present-day distribution of flightless birds suggests that these birds originated from a common ancestor on Gondwana and that the different populations evolved on the isolated southern continents as they drifted apart.

Question 95

What are the 2 main methods used to date a fossil?

Answer 95

1. absolute dating methods
2. relative dating methods

Question 96

What is the absolute dating method used for dating fossils?

Answer 96

Absolute dating methods that tell us the actual age (in years) of an object. There are many absolute dating methods. Nearly all of these methods make use of radioactive elements thatoccur naturally in various types of minerals and organic matter.

Question 97

What is the relative dating method used for dating fossils?

Answer 97

Relative dating methods that can only tell us whether one object is older or younger than another – they cannot pinpoint an actual age in years. Relative dating methods are used to work out thechronological sequence of fossils. They can be applied to fossils found at a particular site and can also be used to make comparisons between sites.

Question 98

List 2 examples of modern evolutionary change:

Answer 98

1. Cane toad
2. Antibiotic-resistant strains of bacteria

Question 99

How has evolutionary change aided the cane toad?

Answer 99

Research found that toads with longer legs move faster and are the first to arrive in new areas. They also found that toads at the front have longer legs than those in older (long-established) populations. These long-legged toads also had more endurance, travelling about half a kilometre further in a three-day period.

The research demonstrated that these changes in a toad’s body shape, its behaviour, dispersal ability and tactics are heritable. That is, offspring resemble their parents, even if they have been raised under standard conditions.

These findings indicate that evolutionary forces are likely to fine-tune organism traits in ways that facilitate more rapid expansion of the invading population, and that control efforts against feral organisms should be launched as soon as possible, before that invader has time to evolve into a more dangerous adversary.

Question 100

How has evolutionary change aided the antibiotic-resistant strains of bacteria?

Answer 100

Antimicrobial Resistance (AMR) occurs when bacteria, viruses, fungi and parasites no longer respond to antimicrobial medicines. As a result of drug resistance, antibiotics and other antimicrobial medicines become ineffective and infections become difficult or impossible to treat, increasing the risk of disease spread, severe illness, disability and death.

AMR is a natural process that happens over time through genetic changes in pathogens. Its emergence and spread is accelerated by human activity, mainly the misuse and overuse of antimicrobials to treat, prevent or control infections in humans, animals and plants.

Question 101

Define the term species?

Answer 101

a group of organisms that can interbreed to produce fertile viable offspring

Question 102

Define the term population?

Answer 102

a group of organisms of the same species, living in the same area at the same time.

Question 103

Define the term community?

Answer 103

a group of populations living and interacting with each other in an area.

Question 104

Define the term habitat?

Answer 104

the environment in which a species normally lives.

Question 105

What is an ecosystem?

Answer 105

a community and its abiotic environment

Question 106

What are biotic factors in an ecosystem?

Answer 106

Biotic Factors are the living influences on where an organism lives (eg. Number of predators, number of mates available, number of competitors, number of disease causing organisms, availability of food).

Question 107

What is predation in an ecosystem?

Answer 107

In an ecosystem, predation is a biological interaction where a predator (an organism that is hunting) feeds on its prey (the organism that is attacked).

Predation can reduce the amount of prey within an ecosystem, but the process can have other effects, as well. If predators thrive, they can essentially wipe out a prey population. This impacts other species by leading to an imbalance.

If a population of predators is removed from an ecosystem the prey population multiply which could lead to habitat destruction and then a reduction in the number of prey.

As the population of the prey increases then the predator population will increase. As the predators increase the number of prey decrease.

Question 108

What is intraspecific competition in an ecosystem?

Answer 108

Intraspecific competition is an interaction in population ecology, whereby members of the same species compete for limited resources. This leads to a reduction in fitness for both individuals.

By contrast, interspecific competition occurs when members of different species compete for a shared resource.

There are short and long term consequences for the ecosystem of species competing for resources. There can be changes in the abundance and distribution.

Question 109

What is an example of intraspecific competition?

Answer 109

In a Gannet (type of seabird) colony as the population grows, so the pressure for good nesting sites increases. This can affect the number of eggs that each female can successfully hatch, and so affects the birth rate of the population as a whole.

Question 110

What are symbiotic relationships?

Answer 110

Symbiosis is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasitic. The organisms may be of the same or of different species.

Question 111

What are the 3 types of symbiosis?

Answer 111

1. Mutualism - both species benefit
2. Commensalism - one species benefits, the other is unaffected
3. Parasitism - one species benefits, the other is harmed

Question 112

What is an example of mutualism?

Answer 112

Note: In mutualism both organisms benefit from the relationship.

Turtles can be covered with patches of algae on their back. Fish eat algae off the turtle’s shell. Both species benefit from their association. Here, the fish get a free meal, and the sea turtle gets a clean shell.

Bees gather nectar, which they make into food, benefiting the bees. When they land in a flower, the bees get some pollen on their hairy bodies, and when they land in the next flower, some of the pollen from the first one rubs off, pollinating the plant. This benefits the plants.

Plover birds pick food scraps from between the jaws of crocodiles, cleaning the crocodiles’ teeth in the process.

Question 113

What is an example of commensalism?

Answer 113

Note: Is a relationship where one is advantaged and the other is unaffected.

A shark swimming with remora fish. The shark are unaffected but the fish can feed on any scraps that the shark misses.

Decorator crabs remove small fragments of tissue from sea sponges and uses them as a source of camouflage.

Question 114

What is an example of parasitism?

Answer 114

Note: a relationship between two species where one is benefited ( the parasite) and one is harmed( the host).

Example is a tapeworm living inside the digestive tract. The tapeworm is supplied with food while the person suffers a loss of nutrients.

Ticks infest the skin and fur of host animals (such as humans), feeding off the host and potentially causing disease.

Leeches attach to the skin and drinks the blood of the host animal until fully engorged.

Question 115

What is distribution when measuring populations of organisms?

Answer 115

Distribution - This is where a species is found

Question 116

What is abundance when measuring populations of organisms?

Answer 116

Abundance - Is the number of organisms residing in an area.

Question 117

What is a limiting factor when measuring populations of organisms?

Answer 117

A population will continue to grow in abundance until it is restricted by a limiting factor.

Limiting factors can include lack of space, predators, disease, availability of light.

Question 118

How do you measure populations of organisms?

Answer 118

Abundance (How many)
Taking a count is more accurate but can be time consuming and sometimes not possible. Populations may be large and impractical to count.

Sampling Techniques
% cover
Quadrats
Capture /recapture

Question 119

What is % cover?

Answer 119

Percent cover is a method of determining relative abundance based on the amount of space they take up.

In this method, rather than counting the number of individuals you calculate based on a visual estimate of how much of the sample plot they occupy.

% Cover can be used to estimate immobile species. For example the area is covered with 65% grass.

Question 120

What is a quadrat?

Answer 120

Quadrats (small squares) are used to estimate the amount of plants and small slow animals. A quadrat is randomly placed within the area and all organisms are counted in the square. This number is then multiplied by the total area ofthe site to get an average.

To place randomly, the quadrat is thrown to fall at ‘random’ within the site.

However, this is usually unsatisfactory because a personal element inevitably enters into the throwing and it is not truly random.

A better method of random sampling is to map the area and then to lay a numbered grid over the map. A (computer generated) random number table is then used to select which squares to sample in.

Question 121

What is the formula to calculate the abundance using quadrants?

Answer 121

Number in quadrat / Area of the quadrat = Number in the total area / Total area

Question 122

What is capture–recapture?

Answer 122

This is good for mobile populations. You capture and tag a sample of the species. They are then released back into the environment and after they have time to mix you recapture a sample and count those that are tagged.

The disadvantage of this technique is that it is expensive, labour intensive, ongoing
monitoring needed, can harm animals and animals may migrate from area.

Question 123

What is the formula to estimate population size using capture-recapture?

Answer 123

Estimated population size = number tagged x number in recapture / number of tagged in recapture

Question 124

How do you estimate distribution (where)?

Answer 124

A transect is a line drawn across an area used to map the occurrence of a species.

Quadrats can also be placed at regular intervals along the transect line in order to generate population data.

A transect line can be made using a nylon rope marked at 1m intervals, all the way along its length. This is laid across the area you wish to study.

Question 125

What is a line transect?

Answer 125

A line transect is where a species touching the line may be recorded along the whole length of the line (continuous sampling). Alternatively, the presence, or absence of species at each marked point is recorded (systematic sampling).

Question 126

What is a belt transect?

Answer 126

This is similar to the line transect method but gives information on abundance as well as presence, or absence of species. It may be considered as a widening of the line transect to form a continuous belt, or series of quadrats.

In this method, the transect line is laid out across the area to be surveyed and a quadrat is placed on the first marked point on the line. The plants and/or animals inside the quadrat are then identified and their abundance estimated. Animals can be counted (if they will sit still!), while it is usual to estimate the percentage cover of plant species.

Quadrats are sampled all the way down the transect line, at each marked point on the line, or at some other predetermined interval (or even randomly) if time is short. It is important that the same person should do the estimations of cover in each quadrat, because the estimation is likely to vary from person to person. If different people estimate percentage cover in different quadrats, then an element of personal variation is introduced which will lead to less accurate results.

This is obviously a very destructive method of sampling which could not be used too often in the same place. Sampling should always be as least destructive as possible and you should try not to trample an area too much when carrying out your survey.

Question 127

What is extinction?

Answer 127

Extinction is the death of a species or group of organisms.

Low level (background) extinction occurs continuously as a species becomes extinct due to specific conditions. Although extinction is a natural phenomenon, it occurs at a natural “background” rate of about one to five species per year.

Mass extinctions is the extinction of many species on a global scale at one period of time.

Question 128

What is an example of a mass extinction event?

Answer 128

During the Pleistocene about 20 000 years ago megafauna became extinct. Megafauna were large animals including giant kangaroos, python, birds, and wombats.

Example:
MEGAFAUNA
Diprotodon was one of Australia’s largest megafauna. There were several species that become extinct about 30,000 years ago - 25,000 years ago. It is the largest marsupial that ever lived.

Many different species of megafauna lived in Australia (and elsewhere around the world) during the Pleistocene Epoch (1.8 million to 12 thousand years ago). Today, Africa still retains many of its megafauna, but in other continents, most megafauna are now extinct

What caused their extinction?
Several theories some believe that they were unable to survive the last ice age, increasing aridity and frequency of fires caused a change in vegetation and these large animals were not able to find food.

Some suggestion that hunting by Aboriginals and their use of fire was a factor.

Question 129

How do you improve the reliability of the data in an experiment?

Answer 129

To improve the reliability of the data you need to repeat the experiment as many times ( more than 10 HSC)possible then average the results. You do not simply do the recording once as it could be inaccurate.

Question 130

What are qualitative observations?

Answer 130

Qualitative observations: based on personal opinion to describe results of an investigation. Qualitative data is information about qualities; information that can’t actually be measured.
Examples include: describing the colour or smell of something.

Question 131

What are quantitative observations?

Answer 131

Quantitative observations: observations that are based on data that is collected using a form of scientific equipment. It is information about quantities; that is, information that can be measured and written down with numbers. Some examples of quantitative data are your height, your shoe size, temperature, measuring distance or using a data logger.

Question 132

What is validity in an experiment?

Answer 132

Validity describes whether the results of an experiment really do measure the concept being tested. A valid experiment is a fair test. A method is valid if:

It investigates what you think it will investigate (i.e. the procedure actually tests the hypothesis and the experiment includes an appropriate range of values).

It incorporates suitable equipment (e.g. measuring cylinder to measure volume rather than a beaker) variables are controlled

Appropriate measuring procedures are included.

Question 133

What is accuracy in an experiment?

Answer 133

Accuracy depends on the design of the experiment (i.e. the validity of the method) and the sensitivity of the instruments used. Results are accurate if:
- The design of the experiment is valid and the sensitivity of the equipment used.
- They are close to the true value of the quantity being measured.
- They can be substantiated in secondary sources.

Question 134

What is an ecological niche?

Answer 134

A niche is the sum total of a species use of the biotic and abiotic resources in its environment.

It consists of all physical and biological conditions which determine the organism’s survival and reproductive prospects.

An ecological niche will be comprised of various components, including:
The habitat in which an organism lives.

The activity patterns of the organism (e.g. periods of time during which it is active).

The resources it obtains from the environment (e.g. food sources, territorial boundaries, etc.)

The interactions that occur with other species in the community (e.g. predator prey relationships, competition, etc.)

Question 135

What is paleontological evidence?

Answer 135

Often the appearance of fossils gives us clues to the climate and environment at the time. Eg. some crocodile species are found only in warm environments and certain plankton in cool.

eg. The discovery of 3.5 bya Precambrian fossils from Marble Bar Western Australia provide some of the first evidence of the nature of past ecosystems on Earth.

Microfossils of single celled filamentous anaerobic prokaryotes were found.

When scientists examined their features they were found to closely resemble modern examples living today in volcanic hot springs.

From this it can be inferred that these organisms lived in a hydrothermal environment. Scientists can infer that chemosynthesis may have been the easiest way that organisms built organic molecules even before photosynthesis.

Question 136

What are fossils?

Answer 136

Fossils are the remains of living things or evidence of their past existence.

Question 137

How can aboriginal rock paintings be used as evidence for past changes in ecosystems?

Answer 137

Aboriginal and Torres Strait Island people have lived in Australia for more than 65,000 years and recorded and passed down the history of the land through their culture. One method is rock painting. Some paintings are approximately 20,000 years old. Some rock art shows extinct species, such as megafauna. This consolidates evidence for the exact period those species were on the earth.

Question 138

How can geological rock structure and formation be used as evidence for past changes in ecosystems?

Answer 138

Fossils preserved in rocks provide a wealth of information about past ecosystems.

Rocks also provide information about past environments and what ecosystems have thrived in them.

Remember: There are three types of rock structures:
- Sedimentary rocks: are created by deposition (placing) of material and often have a sandy texture (eg. sandstone).
- Igneous rocks: are formed from lava spilling either onto land or into the ocean and show a volcanic event in past ecosystem.
- Metamorphic rocks: are formed by metamorphism (a process of changing sedimentary or igneous sediments into a new rock form by extreme heat or pressure). This can give evidence as to how the land has changed.

Question 139

What are banded iron formations?

Answer 139

These are ancient rock deposits that consist of alternate layers of iron rich and silica rich deposits.

At the time of formation the atmosphere did not have any free oxygen and the sea contained large amounts of dissolved iron.

The iron oxide precipitated out of solution forming thin layers on the ocean floor.
Many of the anaerobic life forms in the ocean had skeletons of silica (silicon dioxide). Oxygen was poisonous and killed them in uncountable billions.

As their bodies settled to the ocean floor a silica layer was formed on the layer of iron oxide.

Repeated layers of iron oxide and silica formed the BIFs as seen in Western Australia.

When the first organisms began to photosythesise they gave off oxygen as a waste product.

This oxygen bonded with iron and formed iron oxide.

Coal seams along the east coast of Australia provides information about past environments.

Question 140

How was coal formed?

Answer 140

Coal formed when ancient swamp forests were covered with sediments, water and more plant remains. Under heat and pressure material was compressed and carbonised to form coal seams.

Question 141

How does coal provide evidence for past changes in ecosystems?

Answer 141

Coal formation began about 300 million years ago, during the Carboniferous period. The Earth was covered in wide, shallow seas and dense forests. The seas occasionally flooded the forested areas, trapping plants and algae at the bottom of a swampy wetland. Over time, the plants (mostly mosses) and algae were buried and compressed under the weight of overlying mud and vegetation.

As the plant debris sank deeper under Earth’s surface, it encountered increased
temperatures and higher pressure. Mud and acidic water prevented the plant matter
from coming into contact with oxygen. Due to this, the plant matter decomposed at a
very slow rate and retained most of its carbon. (peat).

Question 142

What is radiometric dating?

Answer 142

Radiometric dating is the process whereby scientists determine the age in years of a fossil, rock or mineral. It measures the amount of radiation produced in a given amount of time.

The unstable parent isotope decays and releases energy and/ or particles to become a more stable daughter atom.

The rate at which this decay process occurs is calculated using an equation (the age equation) that compares the abundance that the naturally occurring isotope in the rock with the abundance of the decay product.

Question 143

What is Darwin and Wallace’s Theory of Evolution by Natural Selection?

Answer 143

Darwin’s theory actually contains two major ideas:

1. One idea is that evolution occurs. In other words, organisms change over time. Life on Earth has changed as descendants diverged from common ancestors in the past.
2. The other idea is that evolution occurs by natural selection. Natural selection is the process in which living things with beneficial traits produce more offspring than others do. This results in changes in the traits of living things over time.

Question 144

What are multicellular organisms?

Answer 144

Multicellular organisms are not simply thousands of cells lumped together . Cells have become organised into groups called tissues. E.g. blood tissue , skin tissue.

A division of labour occurs. Different cell types are structurally suited to carry out different functions. This increases their effectiveness in carrying out their functions. E.g. Some cells are involved in obtaining nutrients whereas others are for excretion

Question 145

List different types of cells?

Answer 145

1. nerve cells
2. muscle cells
3. bone cells
4. gland cells
5. blood cells
6. reproductive cells

Question 146

How does water enter the root of a plant?

Answer 146

Osmosis

Question 147

What is transpiration?

Answer 147

Transpiration is when water leaves the leaves.

As one water molecule evaporates through the stomata another is pulled up the column.

Movement of water from roots through the xylem to the leaves is referred to as the transpiration stream.

Question 148

Explain a mechanism for movement of material in xylem.

Answer 148

Water molecules are cohesive. As water molecules evaporate the next molecules are pulled up the xylem. This is one of the mechanisms that drives the movement of water from roots to leaves.

Question 149

What is the transport system in a plant?

Answer 149

Water moves into the root through the epidermis, which has been modified to increase surface area. The epidermal cells in this region have outgrowths called root hairs, which can be several millimetres long. Water, carrying solutes, moves across the cortex to xylem in the centre of the room which conducts water up to the rest of the plant.

Sugars are transported down the root in the phloem. This process is translocation.

Question 150

What is the transport system in animals?

Answer 150

The system of structures in vertebrates consisting of the heart, blood vessels, and lymphatics, by which blood and lymph are circulated throughout the body.

Question 151

What is the heart?

Answer 151

The heart is an organ that pumps blood throughout the body via the circulatory system. The blood supplies oxygen and nutrients to the tissues and removing carbon dioxide and other wastes.

Question 152

What is in blood?

Answer 152

red blood cells
digested food
white blood cells
waste (urea)
platelets
hormones
plasma
carbon dioxide
oxygen
red blood cells

Question 153

What do red blood cells do?

Answer 153

transport oxygen

Question 154

What is the cardiovascular system?

Answer 154

The circulatory system, also called the cardiovascular system or the vascular system, is an organ system that permits blood to circulate and transport nutrients (such as amino acids and electrolytes), oxygen, carbon dioxide, hormones, and blood cells to and from the cells in the body to provide nourishment and help in fighting diseases, stabilize temperature and pH, and maintain homeostasis.

Question 155

What is the transpiration-cohesion-tension theory?

Answer 155

The hypothesis used to explain how water can travel upwards against gravity in a plant.

Transpiration is the main driver of water movement in the xylem. Water from the roots is ultimately pulled up by this tension. Negative water potential draws water from the soil into the root hairs, then into the root xylem. Cohesion and adhesion draw water up the xylem. Transpiration draws water from the leaf through the stoma. Water potential becomes increasingly negative from the root cells to the stem to the highest leaves, and finally to the atmosphere

Question 156

What evidence has been used to support Darwin’s and Wallaces’ Theory of Evolution by Natural Selection?

Answer 156

SAMPLE ANSWER FOR TEST:
Comparative anatomy has been used to show links between species that seem to have little in common. However, they still have similar features, eg limbs - human hands have 5 digits as do bat wings with 5 digits and horse hoofs. This proves that while species have evolved to suit their environment, they also have a common ancestral link.

OTHER EVIDENCE INCLUDES:
Biochemical evidence
Comparative embryology
Biogeography

Question 157

Give an example of Darwin’s observations and collected data from his voyage around the world.

Answer 157

Galapagos Island Finches - these birds had links to their original ancestor, but also had new features that allowed them to survive in their new environment. They changed their beak size and shape to suit the food source.
Flora and Fauna in Australia - organisms such as platypus changed over time to suit the ecologic of Australia.

Question 158

What technologies have been used to provide evidence for past ecosystem changes?

Answer 158

1. radiometric dating: Radiometric dating is the process whereby scientists determine the age in years of a fossil, rock or mineral. It measures the amount of radiation produced in a given amount of time.

The unstable parent isotope decays and releases energy and/ or particles to become a more stable daughter atom.

The rate at which this decay process occurs is calculated using an equation (the age equation) that compares the abundance that the naturally occurring isotope in the rock with the abundance of the decay product.

2. gas analysis: Scientists can use the data in ice cores to reconstruct atmospheric concentrations of certain gases, particularly carbon dioxide and oxygen.

The gas bubbles are still locked up in the ice when an ice core is retrieved. By melting or crushing the ice, the samples of past atmospheric air can be released from the ice and analysed.

Scientists can use the data in ice cores to reconstruct atmospheric concentrations of certain gases, particularly carbon dioxide and oxygen.

The levels of carbon dioxide in the atmosphere have long been recognised as a key factor in the temperature of the atmosphere.

The gas bubbles are still locked up in the ice when an ice core is retrieved. By melting or crushing the ice, the samples of past atmospheric air can be released from the ice and analysed. In this way, the composition of the atmosphere can be determined hundreds of thousand years back in time.

Question 159

Create a flowchart to trace the digestion of food in the mammalian digestive system and the different process of which it undergoes.

Answer 159

Physical digestion
Chewing with teeth to create smaller pieces of food to be swallowed and digested.
Then:
Chemical digestion
Saliva, enzymes and other digestive juices (such as stomach acid) further break down the pieces of food.
Then:
Absorption of nutrients
The previous steps have turned food into simple carbohydrates, protein, fats, vitamins, minerals and water. These nutrients need to be absorbed into the body via specialised cells in the small intestine and then transported around the body via the blood circulatory system for use in growth, repair and reproduction.
Then:
Elimination of waste
Solid materials that have undergone the process of digestion and have no further nutritional value are excreted via the anus and removed from the body as focal matter.