B5.2 - Natural Selection & Evolution Flashcards
Evolution
The gradual change in a species over time
Natural selection
Process by which species best suited to their environment will survive and reproduce(evolve), passing on their advantageous characteristics to offspring
Summarise the process of evolution by natural selection
- organisms in species show genetic variation (differences in their genes) = range in phenotypes (mutations)
- organisms with characteristics best adapted to environment survive & reproduce, less well adapted organisms die (= survival of the fittest)
- genes from successful organisms passed to offspring in next generation, offspring likely to posses characteristics that made their parents successful
- this process repeated many times, over period of time can lead to development of new species
Peppered moths evolution & natural selection
- before most peppered moths were pale, so camouflaged against trees
- mutation occurred making some moths dark, easily seen by birds & eaten
- pale moths survived & reproduce, so more common
- during industrial revolution, trees become covered in soot, turning bark black
- black moths now camouflaged & survived, pale moths were eaten
- after several years, dark peppered moths become more common in urban areas
Antibiotic-resistant bacteria natural selection
- bacteria reproduce rapidly so evolve in short time frames
- if mutation occurs, bacterium usually dies
- occasionally mutation may be advantageous
(eg. resistance to antibiotic so not killed, bacterium reproduce, passing on antibiotic resistance while antibiotics kill non-resistant bacteria) - eventually may result in whole species becoming antibiotic resistant
Fossils
Formed when animal & plant remains are preserved in rocks
Fossil record = fossil layers form a sequence showing organisms that gradually changed over time
How do fossils form
- reptile dies & falls to ground
- flesh rots, leaving skeleton to be covered in sand/soil/clay before it’s damaged
- protected, over millions of yrs, skeleton becomes mineralised & turns to rock
- rocks shift in earth with fossil trapped inside
- eventually, fossil emerges as rocks move & erosion takes place
How does the fossil record provide evidence for the theory of evolution
- simple life formed gradually evolved into more complex ones: fossils of simplest organisms found in oldest rocks but more complex in recent rocks
- animals require plants to survive: plant fossils appear before animal fossils
- modern day species related to species now extinct, closely related organisms have evolved from same ancestor: studied similarities in anatomy (bone structure)
What are the gaps in the fossil record
- many organisms are soft-bodied & decompose quickly before they fossilise
- many other fossils have been destroyed (volcanic eruptions)
- some fossils waiting to be discovered
Other evidence for evolution
- rapid changes in a species (bacteria replicate rapidly, can study evolution in action)
- extinction (species that don’t adapt to environmental changes die out)
- molecular comparison (comparing DNA and proteins of different species, closely related species have most similar DNA & proteins)
Classification
Process of sorting living organisms into groups to:
- identify species
- predict characteristics
- find/show evolutionary links
- scientists can share their research worldwide
7 taxonomic levels arranged into a hierarchy (classification system)
Kingdom : plants, animals, fungi, protoctista, prokaryotes Phylum Class Order Family Genus Species
Species
Group of organisms able to reproduce to produce fertile offspring
- smallest units of classification
- each group only contains 1 type of organism
Artificial classification
Grouping of organisms based on observable characteristics
Don’t take evolutionary relationships into account
Disadvantages of artificial classification
Difficulties in accurate classification
Eg. Wild roses have 5 petals, so all flowers with 5 petals will be classified as roses
