Biology B1 (part 2)

• Desert Animals: adapted to save water & keep cool
• Large surface area to volume ratio > lose body heat
• Efficient with water > produce small amounts of concentrated urine, produce little sweat
• Good in hot conditions > thin layers of body fat & thin coat > lose body heat
• Camouflage > avoid predators/ sneak up on prey (eg. sandy colour)

• Arctic Animals: adapted to reduce heat loss
• Small surface area to volume ratio > compact rounded shape > reduce heat loss
• Well insulated > thick layer of blubber (also acts as energy store), thick hairy coats, greasy fur (sheds water, prevent evaporation)
• Camouflage > avoid predators/ sneak up on prey (eg. white fur)

• Desert Plants: adapted to having little water
• Small surface area to volume ratio > because they lose water vapour from leaf surface, spines instead of leaves (reduce water loss)
• Water storage tissues > eg. cacti stores water in thick stem
• Maximise water absorption > shallow extensive roots (SA) or deep roots (underground water)

Plants & animals adapted to deter predators

• Armour > thorns (roses), sharp spines (cacti), shells (tortoises)
• Produce poisons > eg. bees and poison ivy
• Warning colours > eg. wasps

Extremophiles

• Microorganisms (eg. bacteria) adapted to live in extreme conditions, like in hot volcano vents, salty lakes or at high pressure on the sea bed

• Organisms Compete for Resources to Survive: (with other species and their own)
  • Plants need light, space, water, minerals (from soil)
  • Animals need territory, mates, food, water

• Environmental Change caused by...
  • Living factors > increase/decrease in infectious disease, change in number of predators, change in number of prey or availablilty of food sources, change in amount/type of competitors.
  • Non-living factors > change in average temperature, change in average rainfall, change in level of air or water pollution

• Environmental Change Affects Populations
  • Population size increase > eg. more prey = more food for predators = survive & reproduce = population increase
  • Population size decrease > eg. bee population fall (pesticides, less food, more disease)
  • Population distribution change (where they live) > eg. distribution of bird species due to rise in temperature

Using Living Indicators...

• Indicator species: organisms that are very sensitive to changes in their environment
  • Air pollution > lichen are sensitive to the concentration of sulphur dioxide in atmosphere, number/ type of lichen in a certain area will indicate how clean the air is
  • Raw sewage released into river > bacterial population will increase & use up oxygen, some invertibrates are sensitive to concentration of dissolved oxygen in water
  • Other invertibrates have adapted to live in polluted conditions (high population indicates  bad pollution)

Using Non-living Indicators... (finding out about environmental change)

• Satellites > measure temperature of sea surface, amount of snow & ice cover
• Automatic weather stations > measure atmospheric temperature
• Rain gauges > measure average annual rainfall 
• Dissolved oxygen meters > measure concentration of dissolved oxygen in water to measure the level of water pollution

There's less energy and less biomass every time you move up a trophic level in a food chain, and usually fewer organisms too (but not if 500 fleas fed on one fox > therefore it's better to look at biomass)

• Each bar on a pyramid of biomass shows mass of living material in that trophic level
• Eg. 100 fleas would have less biomass than one fox and so it would be pyramid-shaped (unlike if it was a number pyramid)
• The largest bar at the bottom represents the producer 
• The next bar > primary consumer, then secondary consumer... etc.

• Energy from the sun > source of energy for most life on Earth
• Green plants and algae use a small % of this light energy to make food in photosynthesis. This energy is stored in the plant and goes through the food chain, as animals eat them and each other.
• Respiration supplies energy for all life processes (inc. movement). Most energy is lost to surroundings as heat.
• Some material in plants and animals is inedible (eg. bone), so doesn't go to next stage of food chain. & Material and energy are lost from the food chain in organisms waste materials.
• This explains biomass pyramids > most biomass is lost and doesn't make it to the next trophic level. Also explains why food chains arn't usually more than 5 trophic levels.

• Living things > made of materials they take in
• Plants take in CO2, O2, H2, N2 from soil or air > turn them into complex compounds (carbohydrates, fats, proteins) pass through the food chain
• These are returned to the environment as waste products/when they die (decay, broken down by microorganisms & returned to soil > best in warm, moist conditions + O2)
• Stable community > materials taken out balance those put back in (constant cycle)

How Carbon is Recycled...

• All cells contain proteins, carbohydrates & fats (which all contain carbon)

• CO2 present in the atmosphere > taken in by plants in photosynthesis
• Plants digested by animals (carbon becomes part of their proteins, carbohydrates & fats) > animals eaten by other animals

• Waste materials from animals
• Microorganisms & ditritus feeders break down waste materials and dead animals
• Carbon comounds in soil > nutrients taken up by plants

• Organisms respire > CO2 into the atmosphere
• Wood & fossil fuels burned (combustion) > CO2 produced

2 Types of Variation Within a Species: genetic variation & environmental variation

• An organism's characteristics are determined by the genes inherited from their parents
• These genes are passed on in gametes, which the offspring develop from
• Some genes from father, some from mother > combination of genes = genetic variation
• Some characteristics are only determined by genes (in animals: eye colour, blood group & inherited disorders)

• The environment that organisms live & grow in causes differences in members of the same species - environmental variation.
• Characteristics could be affected by climate, diet, accidents, culture and lifestyle
• Eg. a plant grown in darkness may grow tall and spindly with yellow leaves

• However, most characteristics are due to both GENES and ENVIRONMENT
• Eg. body weight, height, skin colour, academic, condition of teeth > all determined by a mixture of genetic and environmental factors

Most cells in the human body have a nucleus > the nucleus conatins genetic material

In the nucleus there are 23 pairs of chromosomes

Chromosomes carry genes and are made up of DNA

A gene is a section of DNA

Sexual Reproduction (produces genetically dif. cells) > where genetic info from 2 organisms (a mother and a father) is combined to produce offspring which are genetically dif.

• The mother and father produce gametes (egg & sperm) > in humans each gamete contains 23 chromosomes (only one of each)
• The egg and the sperm fuse together (fertilisation) to form a cell with the full number of chromosomes (half from mum, half from dad) > therefore the offspring contain a mixture of their parents' genes (variation)

Asexual Reproduction (produces genetically identical cells)

• An ordinary cell can make a new cell by dividing in 2 > the new cell has exactly the same genes as the parent cell
• Only one parent > no genetic variation > offspring are clones
• What happens:  X-shaped chromosomes have 2 identical halves > each chromosome splits in half > a membrane forms around each set > the DNA replicates itself to form 2 identical cells with complete sets of X-shaped chromosomes.
• This is how plants & animals grow and produce replacement cells. Some organisms produce offspring using asexual reproduction (eg. bacteria)

Cloning Plants > Cuttings: Take cuttings from good parent plants, plant them to produce genetically identical copies of parent plant. Produced quickly and cheaply 

Cloning Plants > Tissue Culture: A few plant cells are put in growth medium + hormones, they grow into new plants (clones of parent plant). Produced quickly, in little space, all year

Animal Cloning > Embryo Transplants: Cloned offspring in farming (best cow & bull). Sperm cells taken from prize bull and egg cells from prize cow > artificial fertilisation > embryo develops > split many times (before cells specialise) to form clones. Cloned embryos implanted into other cows > genetically identical calves are born. Lots of 'ideal' offspring can be produced                  

Animal Cloning > Adult Cell Cloning: Unfertilised egg cell taken > genetic material removed (nucleus) > complete set of chromosomes from adult body cell inserted into 'empty' egg cell > egg cell stimulated by electric shock > makes it divide > becomes ball of cells > implanted into adult female (surrogate mother) > clone of original adult body cell.                                          Issues with Cloning - 'Reduced gene pool' most alleles same in population, disease could wipe out whole. - Studying clones, better understanding. - Help preserve endangered species. - Clones may not be as healthy. - Some worry of future human cloning.

Useful gene 'cut' from organism's chromosome using enzymes > enzymes used to cut another organism's chromosome > useful gene inserted - Eg. used to produce insulin (in bacteria)

Transferring Genes into Animals & Plants (useful characteristics): > GM crops have their genes modified, eg. induce resistance to viruses/insects/herbicides. > Sheep have been modified to produce eg. drugs in their milk to treat human diseases. > Gene therapy, replace faulty genes with working ones (genetic disorders like cystic fibrosis)

Controversial Topic: Has potential for treating diseases, increasing food production efficiency. But possibilty of unplanned gene problems being passed onto future generations. 

• GM Crops: Pros + Cons
  • Affect no. of flowers, weeds and insects > reduce farmland biodiversity
  • Not everyone convinced GM crops are safe (allergies)
  • Concern, transplanted genes may get out into natural environment (eg. resistance)
  • GM crops increase yield > make more food
  • GM crops to contain specific nutrients > developing countries
  • They're already being grown in other countries without problems

Organisms can be classified as PLANTS (make their own food, fixed in ground), ANIMALS (move around but can't make own food) or MICROORGANISMS (dif. to animals & plants)

Similarites & Differences between organisms > understanding how they're related and how they interact (evolutionary relationships and ecological relationships)

• Evolutionary: Species with similar characteristics > similar genes > share recent ancestor > closely related > similar habitats
• Genetically different species may look similar > adapted to same habitat (not closely related, evolved from dif. ancestors)
• Evolutionary trees show common ancestors & relationships. The more recent the ancestor, the more closely related the 2 species

• Ecological: Organisms in same environment with similar characteristics (eg. dolphins & sharks) > suggests competition (eg. food source)
• Differences can show predator-prey relationships

Natural Selection - Charles Darwin

• Individuals within a species show variation because of differences in their genes
• Individuals with better adapted characteristics to their environment > better chance of survival > more likely to breed successfully
• Genes are responsible for useful genes being passed onto future generations

Evolution can occur due to Mutations

• A mutation is a change in an organism's DNA
• Most of the time they have no effect but occasionally they can be beneficial by producing a useful characteristic > increasing chance of survival and reproduction
• Beneficial mutation more likely to be passed on by natural selection
• Over time the mutation will accumulate in a population

Darwin's Idea was Controversial at the time

• Went against religious beliefs about how life on earth developed (didn't involve God)
• Darwin couldn't give an explanation for how useful genes/mutations appeared. Weren't discovered until 50 years later
• Wasn't enough evidence to convince scientists

Lamarck 1744-1829

• He argued that if a characteristic was used a lot by an organism, it would become more developed during its lifetime (eg. if a rabbit ran a lot, its legs would get longer)
• Lamarck believed that these characteristics would pass on to next generation

• Only way to find out whose hypothesis was right > find evidence to prove/disprove
• Lamarck's theory was eventially rejected > experiments didn't support it
• The discovery of genetics supported Darwin's idea > it provided an explanation of how organisms born with beneficial characteristics could pass them on