Biology - B2

Classification helps us understand how organisms are related and how they interact with eachother.

• Natural classification: based on the evolutionary relationships and genetic similarities between organisms
• Artificial classification: based on appearance than genes. It is used to identify organisms. 

Living things are divided: KINGDOMS, PHYLUM, CLASS, ORDER, FAMILY, GENUS (the group of closely related species) , SPECIES (organisms which can interbreed to produce fertile offspring)

Difficult to classify organisms into distinct groups because many organisms share characteristics of multiple groups.

When scientists discover new species they have to adapt classification systems. Newly discovered species may fit into multiple groups or not fit into any, hence its hard to place them.

DNA sequencing allows us to see genetic differences between groups. This information can show us how closely related some groups are.

Evolutionary trees show common ancestors between species. The more recent the common ancestor, the more closely related the two species.

Studying lots of characteristics for a large group of organisms involves analysing huge amounts of DNA data and is only really possible thanks to advances in ICT.

A species is a group of organisms which can interbreed to produce fertile offspring.

There are problems with classifying species:

• Some organisms reproduce asexually. This means there is no interbreeding so these organisms don't fit in with the definition of a species.
• If you interbreed a male from one species with a female from another you get a hybrid. Hybrids cannot reproduce therefore it is hard to classify them.
• Evolution is a continuous process. Organisms change and evolve over time, sometimes so much that it will form a new species. It can be hard to classify them.

The binomial system gives animals a two part Latin name and is used by scientists all over the world. It is understood worldwide so confusion is avoided. The name comes from the genus and the species.

Similar species often share a common ancestor making them closely related in evolutionary terms. This gives them similar features.

But sometimes, some closely related species may look very different if they have evolved to live in different habitats, e.g. Camels and Llamas.

To explain the similarities and differences between species you have to consider how they're related in evolutionary terms and the type of environment they've adapted to survive in.

Pyramids of Biomass

Each bar in a pyramid of biomass shows the mass of living material at that stage in the food chain. Biomass pyramids are almost always pyramid shaped as biomass is lost at each stage in the food chain. To construct a pyramid of biomass you use the dry biomass of the organisms - measuring dry biomass can be hard though as you have to kill the organisms to work it out. It can sometimes be hard to construct a pyramid of biomass as some animals feed at more than one trophic level.

Pyramids of Numbers

Pyramids of numbers are similar to pyramids of biomass however they show the number of organisms at each stage of the food chain rather than their mass. Pyramids of numbers can be different shapes to pyramids of numbers. For example - one pear tree will feed many aphids, meaning the pear tree bar would be shorter than the aphid bar.

Energy from the sun is the source of energy for almost everything on earth.

• Plants use a small percentage of the light energy from the sun to make food by photosynthesis. This energy then works its way through the food chain.
• Energy is lost at each stage as its used by animals for respiration and other processes which keep animals alive.
• Most energy is lost to the surroundings as heat and is also lost as waste products (i.e. egestion and Excretion). Waste products and uneaten parts can be the start of a new food chain.
• You hardly ever get food chains with more than 4 or 5 trophic levels as all the energy is usually lost by this point.

Numbers on food chains show how much energy is available at the next level. You can work out how much energy has been lost by taking the energy available at the next level from the energy that was available at the last level.

You can calculate efficiency by using this calculation:

Efficiency = energy available at next level/energy available at previous level x100

Organisms compete to gain the things they need to survive, e.g. food and shelter.

Similar organisms in the same habitat will be in CLOSEST competition, as they'll compete for similar ecological niches.

Ecological niche: How it fits in to its ecosystem. Depends on things like where the individuals live and what they feed on.

Two types of competition:

• Interspecific competition is where organisms compete for resources against individuals of another species
• Intraspecific competition is where organisms compete against individuals of the same species.

Intraspecific competition has a bigger impact on organisms than interspecific as the same organisms have the same needs so they will compete for the same resources, which may be limited.            

• The population of any species is limited by the amount of food available.
• If the population of the prey increases so will the population of the predators.
• However if the population of the prey decreases, so will the population of the predator.

Predator - Prey cycles are always out of phases with each other. This is because it takes a while for one population to respond to changes in another. E.g. it takes time for populations to reproduce.

Parasatic

Parastites live off a host. They take what they need to survive without giving anything back, harming the host.

• For example, tape worms absorb lots of nutrients from the host causing them to suffer from malnutrition.
• Fleas are parasites.

Mutualistic

Mutualism is a relationship where both organisms benefit.

• Cleaner species such as oxpeckers live on the back of buffalo. They eat pests but also alert the animal to any predators.
• Plants are pollinated by insects and in return, get nectar (sweet and sugary)

Adaptations are the features that organisms have to make them better suited to their environment. They can fight for resources more easily and will be more able to survive, reproduce and pass on their adaptations to offspring.

• Specialists: organisms which are highly adapted to survive in a SPECIFIC habitat
• Generalists: organisms highly adapted to survive in a RANGE OF DIFFERENT HABITATS
• In a habitat where conditions are stable, specialists will out compete generalists as they're more suited to the specific conditions. In a habitat where conditions are prone to change generalists will out compete specialists as they are adapted to a range of conditions.

Biochemical adaptations

• Some organisms can tolerate extreme conditions, i.e. a very high or low pH or temperature. Organisms adapted to live in seriously extreme conditions are called extremophiles.
• Extremophile bacteria have enzymes which work at  higher optimum temperatures. These enzymes function best at high temperatures without being denatured.
• Organisms that live in cold conditions have antifreeze proteins which interfere with the growth of ice crystals in the cells stopping them being damaged by ice.

Organisms have adaptations to live in cold environments:

Anatomical adaptations

• Thick layer of blubber and fat - insulates the body and traps heat
• Small surface area to volume ratio - reduce heat loss
• Small ear and lined fur - reduces heat loss
• Counter current heat exchange
  • Found in the extremeties of the body
  • Heat exchanges from the warm blood in the artery to the cold blood in the veins
  • Blood gets cold when travelling to the extremeties and lost to surroundings
  • Areries and veins are placed close to each other, reducing heat loss
  • Blood back to the heart is warmer 

Behavioural adaptations

• Migration to warmer climates
• Hibernation to save energy 
• Animals huddle to keep warm

Organisms have adaptations to live in hot environments:

Anatomical adaptations

• Large surface area to volume ratio, increases heat loss
• Large, thin ears means there's large surface area to volume ratio and the blood flows closer to the surface so that heat loss can be increased
• Fat is stored in one place, which stops the rest of the body being insulated, meaning heat is lost easily

Behavioural adaptations

• Spend time in the shade and underground to minimise amount of heat gain
• They're only active at night to reduce heat gain
• They bathe in water and as the water evaporates heat from the skin transfers to the surroundings

Organisms have adaptations to live in dry environments:

Plants 

• Have a small surface area to volume ratio minimsing water loss
• Thich, waxy layer and spines on the plant, reducing water loss
• Stores water in stems to allow them to survive in drought times
• Shallow extensive roots means water is absorbed quickly over a large area

Animals 

• Animals have specialised kidneys which allow them to produce concentrated urine (with a low water content)
• There are no sweat glands, preventing them from losing water through sweating
• Spending lots of time underground means the air contains more moisture 

Charles Darwin came up with the theory about evolution and the theory of natural selection:

Darwin knew that organisms have to compete for limited resources

He concluded that organisms that are the best adapted would be more successful competitors and would be more likely to survive.

This idea is called 'survival of the fittest'.

The successful organisms that survive pass on their strengths to their offspring and the organisms that are less well adapted would be less likely to survive and will not reproduce.

Over time, successful adaptations become more common in the population and the species changes - it evolves.

Darwin's theory wasn't perfect as he could give a good explanation as to why the characteristics appeared or how organisms passed them on. We now know that adaptations are caused by mutations in DNA as DNA was only discovered 50 years after his theory was published.

• Speciation is the development of a new species.

A species may change so much due to natural selection that it becomes a completely new species. Speciation happens when populations of the same species change enough to become reproductively isolated - they can't interbreed to produce fertile offspring.

This can be caused by geographic isolation:

This is when a physical barrier divides a population of a species meaning the populations cant mix. Mutations create new features in the different populations.

Natural selection spreads the mutations and eventually the species either side of the barrier will be so different they won't be able to reproduce and become reproductively isolated.

Why did people not accept Darwin's theory?

• Darwin's theory went against common religious beliefs about creation meaning religious authorities ridiculed him.
• He also couldn't explain why the adaptations occurred as DNA hadn't been discovered.
• There wasn't enough evidence to support him either.

Lamarck: Conflicting theory of evolution

Lamarck argued that if a characteristic was used a lot by an animal then it would become more developed. He argued that these characteristics could be passed on to the animals offspring. But people soon concluded that acquired characteristics don't have a genetic basis - therefore they can't be passed on to the next generation.

Lamarck's theory was rejected and now people accept Darwin's theory as it has been tested by different scientists and the theory offers explanations for other observations too (plants and animals).

• The whole carbon cycle is powered by photosynthesis.
• In photosynthesis plants convert the carbon from CO2  in the air into sugars. Plants can then incorporate this carbon into other carbohydrates, fats and proteins.
• Eating passes the carbon compounds from the plant to animals in a food chain/web.
• Plant and animal respiration while the organisms are living releases CO2 back into the air.
• When plants and animals die and decay, they're broken down by bacteria and fungi in the soil. These decomposers release CO2 back into the air by respiration as the material is broken down.
• Over millions of years material from dead plants/animals can form fossil fuels. When these are burned, CO2 is released back into the air.

Decomposition is slower in waterlogged/acidic soil.

• This is because the bacteria/fungi that are used to decompose material usually need oxygen to respire and produce energy. Waterlogged soils don't have much oxygen so the decomposers work slower. 
• In acidic soil, the extremes of pH slow down the reproduction of decomposers or even kill them.

Carbon can be recycled in the sea.

Many marine organisms make shells out of carbonates.

When the organisms die the shells fall to the ocean floor forming limestone rocks.

The carbon in these rocks returns to the atmosphere as CO2 during volcanic eruptions

Oceans can be absorb large amounts of CO2 acting as 'carbon sinks'.

The atmosphere contains 78% nitrogen which is unreactive and cannot be used directly by plants or animals.Nitrogen is needed for making proteins for growth.

• Plants get their nitrogen from the soil so nitrogen in the air has to be turned into nitrates before plants can use it. Nitrogen compounds are then passed on in food chains/webs as animals eat plants (and each other).
• Decomposers break down proteins in rotting plants/animals and urea in animal waste into ammonia. This returns nitrogen into the soil.
• Nitrogen fixation is the process of turning nitrogen from the air into nitrogen compounds in the soil which plants can use. There are two main ways in which this happens:
  • Lightning:enough energy in lightning to make nitrogen react with oxygen to give nitrates.
  • Nitrogen fixing bacteria:In roots and soil.                                                       
• Decomposers break down proteins and urea into ammonia
• Nitrifying bacteria turn ammonia in decaying matter into nitrates                          
• Nitrogen fixing bacteria turn atmospheric N2 into nitrogen compounds.
• Denitrifying bacteria turn nitrates back into N2.                                                                 

Human population increase is increasing exponentially (extremely quickly). Population increases when the birth rate is higher than the death rate. This growth in population is putting pressure on the environment - more resources are being used up and more pollution produced. The more developed countries in the world use lots of resources and create pollution.

•  Increasing pollution is causing global warming. When more fossil fuels are burned, they release lots of CO2 which is a greenhouse gas. These gases trap heat in the atmosphere and cause global temperatures to rise. Scientists predict that global warming will cause sea levels to rise, weather systems to become less predictable and agricultural output to fail.
• The burning of fossil fuels releases a gas called sulphur dioxide. This reacts with water in the atmosphere to form sulphuric acid which falls as acid rain. Acid rain damages soil and kills trees. Acid rain also raises the pH in lakes, damaging eco systems as many organisms are sensitive to changes in pH. It also damages limestone.
• CFCs are used in aerosols and fridge coolants etc. They break down the ozone in the upper atmosphere allowing harmful UV rays to reach the earth's surface. This increases the risk of acquiring skin cancer and kills plankton in the sea effecting the ecosystem as plankton are at the bottom of the food chain, eventually effecting us. 

Looking for indiactor species can tell you whether an area is polluted or not. 

• Lichen monitor air quality - the cleaner the air, the diversiy of lichen that survive
• Mayfly larvae monitor water quality - the cleaner the water, the more mayfly survive
• Water lice, rat-tailed maggots and sludgeworms indicate polluted water
  • Rat tailed maggots and sludgeworms indiacte a high level of pollution

Meausre pollution:

• Do a simple survey to see if they're present or absent
• Count the number of times an indicator species occurs in an area and give it a numerical value, allowing measurements to be compared
• Use sensitive equiptment to measure the concentrations of chemical pollutants
• Satellite data used to indicate pollutant levels (where the ozone layer is thin - CFC levels)

Living methods - Advantages:

• Using living methods is relatively quick, cheap and easy way of identifying pollution. No expensive equipment is required or highly trained workers needed.

Living methods - Disadvantages:

• Factors other than pollution can influence the survival of indicator species so living methods aren't always reliable

Non-living methods - Advantages:

• Directly measuring the pollutants gives numerical, reliable data that's easy to compare between different sites.
•  The exact pollutants can be identified

Non-living methods - Disadvantages:

• Non-living methods require more expensive equipment and trained workers than methods

Endangered species have risks of becoming extinct if the following factors fall below critical level:

• The number of habitats: hard for organsims to find resources like food and shelter
• The number of individuals: if only a few, hard to find mates and won't be genetic variation
• Genetic variation: (number of differet alleles in population): if genetic variation is low, it'll be hard for them to adapt to changes in the environment or survive in a new disease

Conservation programmes are designed to help save endangered plants and animals. You can evaluate how successful one of these programmes is likely to be by looking at:

• Genetic variation: the species being conserved should have enough genetic variation to survive the appearance of new disease.
• Viability of populations: populations should be able to reproduce so they need both males and females of reproductive age. Need large enough populations to prevent inbreeding 
• Available habitats: there should be plenty of suitable habitats to live in. This is especially important if the organism is a specialist. 
• Interaction between species: Species need interaction as they would in natural environment. 

They help wildlife and humans:

• Protecting the human food supply - over fishing has greatly reduced fish stocks on the world's oceans, conservation programmes ensure future populations will have fish to eat
• Ensuring minimal damage to food chains - if one species becomes extinct it will affect all the other food chains, so the whole food chain is affected. This means conserving one species will help other survive
• Providing future medicines - many medications come from plants these days. Undiscovered plants may contain new medicinal chemicals. When these plants are destroyed in deforestation, we lose chances to discover these
• Cultural aspects - some species may be important in a country's heritage

As human population increases:

• We need to produce more food - more land for farming
• We need more energy - meaning we burn more fossil fuels which are rapidly running out
• Producing more waste - which is polluting the Earth

Sustainable development means providing for the needs of today's increasing population without harming the environment.

Sustainable development needs to be carefully planned out.

• Fishing quotas have been introduced to stop certain species such as cod from becoming extinct

• There are laws which state that logging companies must plant trees to replace the trees they cut down. 

Educaion is important so if people are aware of the problems, they will help. Sustainable development also helps endangered species by considering impacts on their habitats.

• Whales have commercial value, dead or alive
• They're a tourist attraction
• Whale meat and oil can be used and cosmetics made from their waxy substance in their intestines. But this has lead to endangerment. 
• The International Whaling Comission (IWC) has struggled to get nations to restrict whaling. The finally declared a stop to whaling, apart from Norway. But, taking a small number of whales ('culling') for scientific research is allowed. 
• But its hard to check that countries are sticking to the agreement, and even if caught IWC doesn't have the authority to enforce a punishment. So illegal whaling goes on
• Some whales are kept in captivity - there are different views:
  • Whales don't have much space in captivity and are used for entertaining people. Some people think its wrong that they lose their freedom and they would be much happier in the wild, but captive whales increase awareness
  • Captive breeding programmes allow whales to be bred in numbers then put back in the wild
  • Research help us understand their needs better to help conservation, as we don't fully understand them