//b/2/./2// Flashcards
(16 cards)
- When did life on earth approximately begin?
3500 million years ago
- What did life on earth evolve from?
from very simple living things, into more varied and complex forms of life
- Is there variation between individuals in the same species?
yes
e.g. hair colour, height
- Can variation between individuals in the same species be passed onto offspring?
genetic variation can be passed on to offspring
- What causes genetic variation?
changes that occur in genes (mutations)
- What can genetic mutations be caused by?
- outside factors (e.g. radiation, chemicals)
- mistakes when genes are copied in cell division
- What happens when genes are mutated in sex cells?
- will have more effect than if in body cells
- can be passed on to offspring
- can cause offspring to develop new characteristics (which can be harmful or help them survive)
- What happens if genes are mutated in body cells?
- little or no effect to characteristics
- can lead to cancer
- What is the process of natural selection?
-organisms show genetic variation
-resources for survival are limited so individuals’ must compete to survive
-some varieties will have better chance of survival in a species
-these varieties will have more chance of reproducing and passing on their genes
-this will increase the number of individuals displaying the beneficial characteristics needed to survive in later generations
Over generations the ‘best’ features are naturally selected so the species is better adapted to its environment and can survive better
- What is selective breeding?
Selective breeding is when a human deliberately chooses a feature that they want in the next generation of a species and only breeds the organisms that have that feature
- What are the similarities and differences between natural selection and selective breeding?
Natural selection :
- Promotes only features that help survival
- Traits are chosen naturally
Selective breeding :
- Can promote features that don’t help survival
- Traits are chosen with human interference
Both:
- Traits are inherited by parents
- Results in a change in genetics
- The changes can occur over many generations
- What can produce new species in the process of evolution?
Combined effect of:
- Mutations : Different mutations create new features in the two groups of organisms
- Environmental changes : Species in areas with a changed climate will adapt differently to better survive
- Natural selection : New beneficial features will spread through each population
- Isolation : They are separated and can’t inbreed. They may be exposed to different factors (above)
- What is the evidence for evolution?
-The fossil record: Shows complexity of species increasing with time
-Analysis of similarities and differences in the DNA of organisms:
DNA controls characteristics of living things
It changes and mutates over time
if many similarities in DNA, organism evolved from same thing
the more similar the DNA, the more closely related the species
- What was Darwin’s theory of evolution by natural selection a result of?
many observations and creative thought
- What was Lamarck’s theory?
- if a characteristic was used a lot by the animal, it would become more developed
- these acquired characteristics would be passed onto offspring
- Why is Darwin’s a better explanation than Lamarck’s?
- Lamarck’s theory doesn’t fit in with advances in understanding of genetics
(Acquired characteristics have no genetic basis so can’t be passed on to offspring) - There is no evidence or mechanism for acquired characteristics
