Genes Flashcards
What are 2 sources of evidence for evolution?
Fossil Record, Antibiotic Resistance in Bacteria
What is the process by which organisms evolve known as?
Natural Selection
What is the theory of natural selection?
Natural Selection is the process by which organisms change over a period of time; the best adapted organisms pass on their genes; the least adapted animals do not pass on their genes and die out
What is meant by extinction?
When no more individuals of a species remain anywhere in the world
Give five causes of extinction
Changes to the environment Destruction of habitat Disease New predators Increased competition
Explain what is meant by biodiversity
The variety of all the different species of organisms on Earth, or within an ecosystem
What is causing biodiversity to be reduced?
The human population is expanding therefore requiring more space and resources, thus destroying habitats and availability of food for other species
Why is biodiversity essential for populations?
The greater the variation within a species, the more likely the species will survive a change in enviroment
Give 4 different methods to help maintain diversity
Breeding programmes for endangered species
Protection and regeneration of rare habitats
Reduction of deforestation and Co2 emissions
Recycling resources rather than dumping them in landfill sites
What is conservation?
The protection of a natural environment to ensure that an organism’s habitat is not lost
What are two disadvantages of captive breeding?
Gene pools are small so maintaining genetic diversity is difficult, some organisms will not be suitable to be released into the wild
What is a gene bank?
Stores of genetic information from different species to either be used in research in the future or to produce new individuals
How many chromosomes does a human have?
46
Where is the genetic information of a human inherited from?
Half of the information is from the mother, half is inherited from the father
What is a gene?
A gene is a section of a chromosome that holds the information for a particular characteristic
What does DNA stand for?
Deoxyribonucleic acid
What shape is DNA?
A double helix
Name the organelle where DNA is found in a cell
DNA is contained in structures called chromosomes within the nucleus
Describe the structure of DNA
DNA is a polymer made up of two strands forming a double helix
What is an allele?
A different form of the same gene
Explain what is meant by a dominant allele
The characteristic is always expressed even if there is only one copy of the allele
Explain what is meant by a recessive allele
The characteristic will only be expressed if there are two copies of the allele present
Why do humans have two alleles of each gene?
Because one allele is inherited from each parent
How is a dominant allele different to a recessive allele?
Dominant alleles can be expressed when with a recessive allele but a recessive allele needs to be with another recessive allele
How can you predict the likelihood of a characteristic being expressed in a child?
By putting the parent’s alleles into a punnet square
What is genetic modification?
The altering of an organism’s genes to produce an organism with a specific characteristic
What are the negatives of genetic modification?
It is viewed as unethical
There may be unwanted risks of negative health effects
The chance of new pathogens being created
Define the word species
A group of organisms which can be interbreed to make fertile offspring
Give three reasons for variation within a population
Genetic variaton
Enviromental factors
Combination of both genetic and enviromental factors
Define the word evolution
The change in inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species
Describe how fossils can be formed
Fossils are remains of organisms from millions of years ago which are found in rocks
They are formed from parts of organisms that have not decayed and are replaced by minerals as they decay
Describe what is meant by extinction
Extinction occurs when there are no remaining individuals of a species still alive
Complete the order for the classification of animals
a. Kingdom
b. Phylum
c. Class
d. Order
e. Family
f. Genus
g. Species
