Biology Unit 1b

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  • Created by: Zoe
  • Created on: 04-04-13 21:07

Adaptations- Desert and arctic animale

When organisms have particular characteristics that helps them to survive in their environment.

Desert animals have adapted to save water and keep cool

  • Large surface area: lose more body heat to keep cool
  • Efficient with water: lose less water by producing small amounts of concentrated urine and making very little sweat
  • Good in hot conditions: Thin layers of body fat and a thin coat helps lose body heat
  • Camoflague: sandy colour helps them advoid predators

Artic Animals have adapted to reduce heat loss

  • Small surface area compared to volume: compact shape reduces heat loss
  • Well Insulated: thick layer of blubber for insulation-acts as an energy store when food is scarce and a thick,greasy coat keeps heat in and sheds water
  • Camoflague:white furs helps advoid predators
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Adaptations-Desert plants and deterrence

Desert Plants have adapted to having little water

  • Small surface area compared to volume: Lose water vapour from their leaves and their small surface area compared to their size. Cacti have spines instead of leaves
  • Water storage tissues: For example, cactus stores water in its thick stem
  • Maximising water absorption: Some cacti have shallow but long roots to absorb water quickly over a large area

Some Plants and Animals are adapted to deter predators

Various special features used by animals and plants help protect them against being eaten

  • Some have armour- roses:thorns,cacti:spikes and tortoises:shells
  • Some produce poisons- bees and poison ivy
  • Some have warning colours to scare off predators- wasps

Microorganisms have a huge variety of adaptations so they can live in a wide range of enviroments e.g: extremophiles are adapted to living in seriously extreme conditions like very hot volcanic vents

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Compertition and Enviromental change

Organisms compete for resources to survive

Animals

The resources that animals compete for include:

  • food
  • water
  • space.

Animals may also compete for mates so that they can reproduce.

Plants

Remember that plants make their own food using photosynthesis, so they do not compete for food. The resources that plants compete for include:

  • water
  • space
  • mineral salts.
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Enviromental changes

Enviromental changes are caused by different factors

Changes are caused by living and non-living factors, such as:

Living:

  • Change in the Occurrence of infectious diseases
  • Change in the number of predators
  • Change in the number of prey or the avaliability of food sources
  • Changes in the number or types of competitors

Non-living factors:

  • A change in the average temperature
  • Change in the average rainfall
  • Change in the level of air or water pollution
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Enviromental Changes 2

Enviromental changes affect populations in different ways

Population Size Increase

  • If the number of prey increases, then there's more food avaliable , so more predators survive and reproduce and their numbers increase

Population Size decreases

E.g the number of bees is falling rapidly because of:

  • Some pesticides may be having a negative effect on bees
  • less food avaliable- arent as many nectar rich plants
  • More diseases- new pathogens or parasites killing bees

Population Distribution changes

  • A change in distribution means a change in where an organism lives
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Measuring Enviromental change

Enviromental changes can be meaured using living indicators

Some organisims are sensitive to changes in the enviroment can be studied to see the effect of human activity- Indicator Species

  • Air pollution can be monitored by looking at different types of lichens- they are sensitive to the sulfur dioxide concentration in the air so give a good idea about pollution levels. The number and type of lichen at a particular location indicates how clean the air is
  • Raw sewage in rivers causes the bacterial population to increase and uses up the oxygen. Mayfly larvae are good indicators for water polution because they're very sensitive to the concentration of dissolved oxygen in the water- indicates the water is clean

and Non-living indicators:

  • Satellites: measure temperature of the sea surface and the amount of snow and ice cover- gives global coverage about enviromental changes
  • Automatic weather stations tell us the atmospheric temperature at different locations
  • Measure rainfall using rain gauges to see if the average rain fall changes
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Pyramids of Biomass

The dry mass of an organism is called its biomass. The total biomass at a particular step in a food chain is always less than the total biomass at the step before it. Let's look again at the food chain:

grass → vole → barn owl

The biomass of all the grass plants is the greatest in the chain, and the biomass of all the barn owls is the least. We can show information like this using a pyramid of biomass.

oak tree → caterpillar → blue *** → sparrow hawk

Oak trees are very large, but caterpillars are very small. One oak tree can feed many caterpillars, but many caterpillars are needed to feed a blue ***, and many blue ***s are needed to feed a sparrow hawk.

The wider the bar, the more biomass there is. Pyramids of biomass always have this shape (but pyramids of numbers can be any shape).

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Pyramid of biomass

From the bottom of the pyramid up: oak tree, caterpillar, blue ***, sparrowhawk. This is a regular pyramid shape as the base is wide and the top narrow. (http://www.bbc.co.uk/schools/gcsebitesize/science/images/23_2_pyramids_of_biomass.gif)

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Decomposition

The cells and bodies of plants and animals decay by the action of soil bacteria and fungi. They are often called the decomposers.

The molecules released during decay are absorbed by the bacteria, fungi and also back into the soil from where plants can draw them up through their roots.The decomposers work best at their optimum conditions since they use enzymes. The kind of conditions needed are shown nicely by the humble compost heap.

There are five necessary conditions or factors for good decomposition:

  1. Organic material: plant or animal material to decay
  2. Water: the right amount of moisture
  3. Oxygen: air must be able to get to the material
  4. Warmth: the temperature cannot be too hot or too cold
  5. Decomposers: bacteria or fungi are needed to do the job

You would not get decomposition if one of these was missing.

The molecules released by this decay process include the most important elements carbon and nitrogen which have their own environmental cycles.

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The carbon cycle

Carbon is passed from the atmosphere, as carbon dioxide, to living things, passed from one organism to the next in complex molecules, and returned to the atmosphere as carbon dioxide again. This is known as the carbon cycle.

Removing CO2 from the atmosphere

Green plants remove carbon dioxide from the atmosphere by photosynthesis. The carbon becomes part of complex molecules such as proteins, fats and carbohydrates in the plants.

Returning CO2 to the atmosphere

Organisms return carbon dioxide to the atmosphere by respiration. It is not just animals that respire. Plants and microorganisms do, too.

Passing carbon from one organism to the next

When an animal eats a plant, carbon from the plant becomes part of the fats and proteins in the animal. Microorganisms and some animals feed on waste material from animals, and the remains of dead animals and plants. The carbon then becomes part of these microorganisms and detritus feeders.

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Variation

Organisms of the same species have differences

  • Organisms of the same species will look slightly different
  • The difference can be:genetic variation and enviromental variation

Different genes cause Genetic variation

  • All plants and animals have characteristics that are similar to their parent
  • Organism's characteristics are determined by the genes inherited from their parents- gene codes inside your cells
  • Genes are passed on through gametes, which the offspring develope from
  • Most get gametes from both the mother and father
  • The combining of genes causes genetic variation
  • Some characteristics are determined only by genes- in animals these include: eye colour,blood group and inherited disorders
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Variation 2

Characteristics are also influenced by the enviroment

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Genes, Chromosomes and DNA

Most cells have a nucleus that contains your genetic material in the form of chromosomes.Nucleus contains 23 pairs of chromosomes.Chromosomes carry different genes which control the development of different characteristics e.g hair colour

A gene is a short lenght of the chromosome. They form DNA molecules which are a long length of DNA. Can be different versions of the same gene e.g blue or brown eyes. The different versions are called alleles.Dna is coiled up to form the arms of the chromosomes

chromosome, showing gene as section of DNA (http://www.bbc.co.uk/schools/gcsebitesize/science/images/cell_chrom_dna.jpg)

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Sexual Reproduction

Sexual reproduction Involves the fusion of male and female gametes because there are 2 parents, the offspring contain a mixture of their parents genes

This method involves the joining of a male sex cell and a female sex cell from two parents. These two special cells (gametes) join to form a new individual.  If you are the result of sexual reproduction you will inherit genetic information from both your parents, so there will be lots of variety in the population.  

the female egg and the male sperm fuse to create a zygote cell which then turns into an embryo. 23 chromosomes from the male and female each make 46 chromosomes in 23 pairs (http://www.bbc.co.uk/schools/gcsebitesize/science/images/9_sex_cells.gif)

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Asexual reproduction

In Asexual reproduction there's only one parent.There's no fusion of gametes, no mixing of chromosomes and no genetic variation between parent and offspring The offspring are genetically identical to the parent

Asexual reproduction involves only one parent and so the offspring is identical and there is no variety. It gives rise to offspring known as clones. Their genetic material is identical to the parent and each other.  

 Asexual Reproduction is very common in the smallest animals and bacteria but it even takes place in your own body, as cells divide and grow to replace worn-out tissues.  

In plants the gametes involved in sexual reproduction are found within ovules and pollen. In animals, they are called ova (eggs) and sperm. In humans each gamete contains only 23 chromosomes – half the number of chromosomes in a normal cell. The egg and the sperm cell then fuse together (fertilisation) to form a cell with the full number of chromosomes. 

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Cloning methods

Plants can be cloned from cuttings and by tissue culture

Cuttings

  • Gardeners take cuttings from good parent plants, plant them to produce genetically identical copies of the parent
  • Produced quickly and cheaply
  • Makes good crops

Tissue Culture

  • A few plant cells are put in a growth medium with hormones, resulting in them growing into new plants
  • Made very quickly
  • Need very little space
  • Grown all year round
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Cloning- Animal clones using embryo transplants

Sperm cells are taken from a prize bull and egg cells are taken from a prize cow. The sperm from the prize bull is then used to artificcally fertilise an egg cell. The embryo developes then splits many times to form clones befor the cells become specialised

The egg cell is stimulated by an electric shock to make it divide

The embryo is then implanted into an adult female to grow genetically identical copies of the original adult body cell

Created Dolly- a famously cloned sheep

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Cloning- Adult cell cloning

Adult cell cloning involves taking an unfertilised egg cell and removing the nucleus (genetic material) A nucleus from a different animal is inserted into the empty egg cell

The egg cell is stimulated by an electric shock to make it divide

The ball of cells is then implanted into an adult female to grow into a genetically identical copy

(http://www.bbc.co.uk/schools/gcsebitesize/science/images/cloning.gif)

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Issues surrounding cloning

There are strong arguments for and against cloning and genetic engineering. It is possible to produce genetically modified animals and plants. Sheep that produce human proteins for treating the symptoms of cystic fibrosis - a disease which causes sufferers to produce abnormally thick and sticky mucus in their lungs - have been produced, and even tobacco plants that glow in the dark when they need watering.

Some people are excited by the almost limitless possibilities of cloning and genetic engineering, while some people believe the process is unethical and should be banned. Others are concerned about what might happen in the future.

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Genetic engineering

Involves changing the genetic material of an organism

You take the gene from one living thing and transferring it to another

Benefits

  • Genes can be added to crops to produce bigger yields
  • They can also be designed to grow well in dry, hot or cold parts parts of the world
  • Crops can be produced that make their own pesticides or are resistant to herbicides

Human Engineering

  • This can be used to help people with a genetic disease e.g cystic fibrosis
  • A couple with a genetic disease can have a baby using ivf
  • The embryo can be engineered so that its free of disease
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Advantages and disadvantages of genetic engineerin

Advantages:

  • Food production- rice has been produced with high amounts of vitamin A
  • treating genetic diseases- this can be used to help people with a genetic disease e.g cystic fibrosis

Disadvantages:

  • Insects may become pesticide-resistant if they eat a constant diet of pesticide forming plants

Worries over genetic engineering:

  • Genes from genetically modified plants and animals could spread into the countryside
  • Genetically modified plants and crops are often infertile
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Designer Babies

When you choose the characteristics of the baby e.g nose,eyes,hair

Problems with designer babies:

  • Apart from having healthy children you might pick desired genes in children e.g intelligence,blue eyes, blonde hair
  • This reduces variation in the gene pool
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Evolution

Darwins theory

  • Theory of evolution by natural selection
  • All living things have variations caused by mutations
  • Everything with the stronger variations will survive and the one's with weaker variations will become extinct
  • Some will have variations better adapted (fitter) than others
  • During enviromental changes the best adapted living things survive and breed
  • Over time living things change as there adaptations are passed on

Why his theory was only gradually accepted?

  • Darwin didnt know about genes
  • It was rejected by creationists
  • He didnt have sufficient evidence
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Evolution 2

What happens when living things are unable to evolve in time?

Extinctions-Can be cause by extreme enviromental changes,disease or humans

If the producer becomes extinct something else in the food chain is affected for example the primary consumer

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