B3- Life On Earth Flashcards
Why are animals adapted to their environment?
Adaptations make individuals of a species more likely to survive and produce offspring- this makes it more likely that the whole species will continue to exist in its environment.
Why do individuals of the small species have differences?
- Differences between species are called variation. Some of this variation is genetic so it can be passed on to the individuals offspring.
- One of the causes of genetic variation is when genes change.
- These changes are called mutations- mutations are caused by outside factors like radiation, chemicals or a mistake during cell division.
What happens if a mutation happens is body cells?
They usually have little or no effect - though they can lead to cancer.
What happens if mutations happen during the formation of sex cells?
They have more effect because the mutation will then be passed on to all the cells of its offspring.
This causes the offspring to develop new characteristics- some of the characteristics are harmful to the organism but some can help them survive.
Describe natural selection?
- Living things show genetic variation.
- The resources living things need to survive are limited. Individuals must compete for these resources to survive- only some individuals survive.
- Some varieties of a particular species will have a better chance of survival. Those varieties will then have an increased chance of reproducing and passing on their genes.
- This means that a greater proportion of individuals in the next generation will have characteristics that help the organism to survive.
- Over years, this species becomes better at surviving. The best features are naturally selected and species become adapted to their environment.
What is selective breeding?
It involves humans purposely choosing a feature they want to appear in the next generation and only breeding from animals and plants who have it.
Selective breeding may promote features that don’t help an organism survive.
How can the process of evolution produce new species?
Sometimes groups of organisms of the same species become isolated from each other so they cannot interbreed.
A number of factors then combine to make the two groups of organisms so different that they can become two different species.
- different mutations create different new features in the two groups of organisms.
- natural selection works on the new feature if they are of benefit they can spread through each of the populations.
- environmental changes help the organisms to adapt to a certain environment (e.g. Weather)
What is the evidence for evolution?
Fossil records and DNA provide evidence for evolution.
Fossil records show species getting more complex as time goes on.
DNA controls characteristics and mutates and changes over time. Thus evolution started from simple life forms and complexed over time.
Who was Charles Darwin?
He proposed the theory of evolution by natural selection. He made observations of organisms and applied creative thought to his findings.
Who was Lamarck?
He was a French man that argued if a characteristic was used a lot by an animal it would become more developed.
Lamarck thought these acquired characteristics could be passed on to the animals offspring.
However, people rejected his theory because acquired characteristics don’t have genetic basis.
What is biodiversity?
It includes;
- the number of different species on the Earth.
- the range of different types of organisms
- the genetic variation between organisms of the same species.
Why is biodiversity important?
The more plants we have - the more resources there are for developing new food crops.
Many new medicines have been discovered using chemicals produced by living things.
Why is the rate of extinction increasing?
There is a correlation between the growth of the worlds population and the number of species extinctions.
This suggests that a lot of extinctions are caused by human activity. Humans kill directly and indirectly- by destroying their habitat or introducing a new species to compete with.
What is classification?
Scientists group similar organisms together.
• there are 5 kingdoms;
Bacteria,fungi,algae,plants and animals.
- each kingdom divides into more groups and they divide again until you get species.
- as you go down these groups the number of types of organisms in each one decreases, but the number of characteristics that the organisms have in common increases.
Why is classification important?
- it shows us evolutionary relationships between different organisms. (They share more genes and characteristics)
- evolutionary relationships can be shown for all living things and fossilised organisms that have been classified.
