Natural Selection #3 Flashcards
(37 cards)
What is Aristotle ladder of life
An ancient concept where all living things are ranked in hierarchy from the simplest to the most complex with humans at the top
What are the key ideas of Aristotle’s ladder
- life forms arranged in a linear scale from least perfect to most perfect
- the ladder reflects a fixed unchanging order (Aristotle didn’t believe in evolution)
- organisms were grouped based on how much soul or purpose they had
Explain the simplified structure of Aristotle’s ladder
- Non living things (rocks)
- Plants (living but no movement or senses)
- Simple animals (can move and sense but not reason)
- More complex animals (like mammals)
- Humans (at top cause of rational thought)
What was aristotles ladder based on and what was it not
Observation and philosophy and not on evolution or genetics
How long was aristotles ladder recognized for
Dominated view for about 2000 years
Who was George Cuvier
French naturalist and palaeontologist who played major roles in developing the field of comparative anatomy and understanding the fossil record
What were Cuvier three main contributions to fossil understanding
- Fossils represent extinct species-
- first to argue fossils are remains of extinct organisms
- showed that some creatures had no living counterparts- they were extinct - Fossil layers and change over time
- noticed that fossils in older rock layers were different to those newer layers - Catastrophism
- he believed earths history was shaped by sudden violent catastrophes (floods or volcanic eruptions)
- these events caused mass extinctions and new species appeared
- he reject evolution and believed that new species were created after each catastrophe
What is Lamarckism
Jean baptiste Lamarck proposed the theory of evolution where:
- species never become extinct
- instead over time they become new (better) species
- offspring inherit characters acquired by their parents
Believed this happened through use and disuse of traits and acquired traits were inherited
What is the key concepts of lamarcks evolution theory (2) and an example
- Use and disuse
- if an organism uses a body part a lot it becomes bigger and stronger
- if a body part is not used it becomes weaker and disappears
Ie, giraffes stretch their necks to reach leaves so their necks grow longer
- Inheritance of acquired characteristics
- changes that an organism acquires during their lifetime and can be passed onto its offspring’s
Ie, giraffe that stretches its necks longer would have babies with longer necks
Natural selection vs survival of the fittest difference
Natural selection- processe by which individuals with traits better suited to their environment survive and reproduce more successfully passing those traits onto the next generation (the differential reproductive success of different phenotypes)
Survival of the fittest- phrase that describes the outcome of natural selection. Who passes on he genes the best
What were lamarcks three additional beliefs
- Use and disuse= Each species was created separately and improved over generations based on use and need
- Separate lineages= He thought lineages remained separate and did not share common ancestors
- Escalators= biodiversity is like a series of escalators, evolving independently and progressively towards a greater complexity
Who came up with the theory of natural selection
Charles Darwin
What did Darwin observe (4)
- More individuals are born than can survive
- There is variation in traits within a population
- Some traits give advantages in survival or reproduction
- Over generations advantageous traits become more common
What were the three important observations made along Darwin’s journey
South America- found fossils of extinct animals and noticed similarities to modern species
Galápagos Islands- Darwin saw different species of finches on each island with beaks adapted to different food
Patterns of biodiversity- he noticed that species seemed adapted to their environments and that similar animals lived in similar habitats even if far apart
Facts about Darwin’s voyage
- 5 years
- HMS beagle
- 1831-1836
- purpose- survey coastlines for British navy but Darwin used the opportunity to collect fossils, plants, animals and geological samples
What did Darwin notice about his finches
- 15 species - common descent
- found on the Galápagos Islands (1835)
- helped develop theory of natural selection
- looked similar but had different beak shapes and sizes
- each beak was suited to a different type of food (seeds, insects, cactus)
- small variation within islands but big difference between islands
What did the variation in finches show Darwin
- species are not fixed, they can change over time
- traits that help survival are passed on in a natural selection action
What was Malthus theory
Struggle for survival
- population grew faster than food supply
- this leads to competition for limited resources like food, space and mates
- as a result not everyone survives
How did Malthus theory influence Darwin
Malthus said populations grow faster than resources, leading to a struggle for survival. Darwin used this idea to understand that in nature, only the individuals with the best traits survive and reproduce which drives natural selection and evolution
Explain Malthus graph
- Population curve
- curves up sharply like a J shape
- population increases rapidly- doubling over time - Food supply curve
- rising straight, steady line
- food increases slowly and evenly over time
Whats the theory of evolution by natural selection
- All species can grow exponentially and produces lots of offspring
- But most populations stay stable in size because of limited food and space
- Individuals vary in traits
- Some of these differences are passed on to their offspring
- The ones with the best traits for the environment survive and have more offspring
- Over time the helpful traits become more common and the species slowly change
Difference between lamarcks and Darwin’s theory
Darwins theory:
- believed individuals born with natural differences
- some traits help them survive and reproduce better
- favourable traits passed on
- natural selection leads to changes in species
- evolution is gradual and based on which trait best suited to environment (bush)
- all species share a common ancestor and evolve
Lamarck’s theory:
- organism could change during their lifetime if needed
- traits used become stringer
- traits not used become weaker
- acquired traits passed to offspring
- evolution was seen as a process of constant improvement (escalator)
- evolved separately without common ancestors
Problems with Darwin’s theory
- He didn’t know where traits were inherited- genes and DNA were not discovered yet
- couldn’t explain where new variation came from
What is modern synthesis (neo Darwinism)
scientists combined Darwin’s theory with mendels genetics- creating modern synthesis
