GCSE AQA BIOLOGY: Evolution and Speciation

What does the theory of evolution state?

The species of all living things that exist today and have gone extinct, have evolved from simple life forms that first developed more than 3 billion years ago.

What did most people believe about life before the 18th century in Europe

Creationism

What is creationism?

The belief that God created the universe as described by the Bible.

When did scientists start challenging creationism?

The early 19th century

What was Jean-Baptiste Lamarck's theory?

The inheritance of acquired characteristics

What is the 1st step of Lamarck's theory for giraffes?

Some giraffes stretched their necks to reach the highest trees

What is the 2nd step of Lamarck's theory for giraffes?

Those giraffes ended up with longer/stretched necks

What is the 3rd step of Lamarck's theory for giraffes?

The giraffes with stretched necks could pass down this acquired characteristic to their offspring

What is the 4th step of Lamarck's theory for giraffes?

Over generations this repeated so more of the giraffe population had longer necks, as this acquired characteristic was more advantageous as those giraffes could reach more food - giving them higher survival and reproduction rates.

Give 3 of Lamarck's ideas?

- all organisms are linked by fountain of life

- every animal evolved from a primitive type of worms

- if an animals feature wasn't used, it would shrink and be lost

What is the benefit of Lamarck's work?

He Influenced Darwin and other scientists to go further with evolution

Give 3 problems with Lamarck's ideas?

- no evidence for the 'fountain of life'

- general distaste for the idea of being descended from worms

- WE KNOW AND CAN CLEARLY SEE THAT IN THE VAST MAJORITY OF CASES 'ACQUIRED' TRAIT INHERITANCE CANNOT OCCUR

The theory of evolution by natural selection

What sparked Darwin's theory?

At 22 in 1831, he set out on a 5 year expedition to the Southern hemisphere on the HMS Beagle.

Which islands impacted Darwin the most?

The Galapagos Islands

What did he find on each island?

Each island had its own type of finch with strong similarities but different beak types

What did the different beak types allow for?

Making them adapted to their environment - food sources

What did Darwin suspect about these finches?

They all originated from 1 species

How did Darwin build his theory?

- observations from the 5 year expedition

- years of experimentation & discussion around geology and fossils

- 20 years refining his ideas back in England

What type of observations did Darwin take?

- specimens (flora and fauna)

- detailed drawings

- written observations

What was Darwin's key observation about characteristics?

Characteristics are inherited from parents

Why was Darwin talking about characteristics?

As the mechanism for evolution - genes - were not discovered until 50 years later

Why is there competition for resources in the world?

More offspring are produced than the environment can support

What type of resources would be competed for?

Food, habitats, mates

What does harsh competition mean for the individuals?

Not all individuals (those with disadvantageous alleles) will survive to adulthood and reproduce themselves

Why were Darwin's ideas controversial?

it went against common religious beliefs, darwin couldn't explain mutations with genes, there wasn't enough evidence

What is the 1st step of natural selection?

Variation of a characteristic exists in a named species' population due to random mutation - resulting in different alleles.

For this 1st step of natural selection what must be mentioned?

What the phenotype/ varied characteristics different individuals must have. (Some individuals have y but other individuals have x)

What does variation in a population lead to?

Some named alleles are advantageous (as the allele allows for...). This means that the individuals with this allele are more likely to survive and therefore go on and reproduce.

What happened when the individuals with the advantageous alleles reproduce?

They pass down their alleles to their offspring

What happen to the process of natural selection?

This repeats over many generations and eventually the advantageous allele with higher survival and reproduction rates becomes more frequent in the named population.

What is a species?

A group of organisms with similar features that can breed and produce fertile offspring.

Who does the species definition not apply to?

Organisms that can reproduce asexually

How can reproduction between different species be prevented?

Genetically or mechanically

Who was developing the same mechanism for evolution as Darwin simultaneously?

Alfred Russel Wallace

What happened in 1958 for Alfred Russel Wallace?

After contact with Darwin, they published joint works

What did Alfred Russel Wallace contacting Darwin prompt him to do?

This led Darwin to publish his book the Origin of the Species in 1959

Why were Wallace's ideas were not as respected as Darwin's?

They weren't as carefully crafted or backed up by years of research

Whilst Wallace travelled the world gathering evidence to support his theory of evolution, what did he work on?

Warning colouration in animals

What were Wallace's most famous works?

Warning colouration in animals and speciation

What is speciation?

The formation of a new species as they evolve form an existing species (and further back common ancestors)

What has led to our current understanding of the theory of speciation?

Wallace's pioneering work and more evidence over time

What is the 1st step of speciation?

There is variation in the original population of a species due to mutation.

What is the 2nd step of speciation?

The population then becomes separated by a named geographical barrier.

After the 2 populations are isolated, what happens?

They experience different environments, so different alleles are advantageous in each environment and are selected for.

How must you specify the differences in environments?

(habitats/predators/food sources/temperatures)

What happens to the individuals with advantageous alleles?

they have higher survivals and therefore reproduction rates, so they can be passed down to offspring.

What is the last step of speciation?

When the 2 populations meet again, they can no longer reproduce with each other. This distinguishes them as separate species.

How is the theory of evolution now received?

It's now widely accepted

What was the main discovery that led to Darwin's idea being accepted?

The discovery of genes 50 years later

What provides further evidence for evolution?

The fossil record and antibiotic resistance

What makes bacteria a good study for evolution?

They reproduce at a very fast rate so they evolve rapildy

What has given some bacteria antibiotic resistance initially?

Mutation

When exposes to an antibiotic in a human what occurs?

Both pathogenic bacteria and healthy gut bacteria are killed

What happens after pathogenic bacteria and healthy gut bacteria die?

There is reduced competition to nutrients, antibiotic resistant bacteria multiply rapidly forming a larger population that is difficult to control.

How can antibiotic resistance be shared?

Bacteria can share plasmids with antibiotic resistant genes between bacteria of both the same and different species

Give 3 methods to reduce antibiotic resistance?

- reduce prescription/overuse of antibiotics unless absolutely necessary

- take antibiotics for the full course

- modify intensive farming practices that overuse soluble antibiotics

Why are there issues with new antibiotics?

They are costly and slow to produce and may not keep up with the emergence of new antibiotic resistant strains of bacteria.

What are fossils?

preserved remains of ancient organisms

What are the 3 processes that fossils can form from?

- mineralisation

- prevention of decay

- preserved traces

What is the 1st step of mineralisation?

The organism dies and sinks to the sea floor. Here, the soft parts of the carcass are eaten or decay.

What is the 2nd step of mineralisation?

The hard parts of the organism (eg. Bones, teeth, claws) are covered by sediment.

What is the 3rd step of mineralisation?

Over time the hard parts (skeleton) dissolve to form a cavity in the exact same shape as the skeleton

What is the 4th step of mineralisation?

Mineral rich water fills the cavity and the minerals crystallise inside the mould - forming a cast.

What is the 5th step of mineralisation?

Millions of years later the rock surrounding the skeleton rises to the Earth's surface and the fossil is discovered.

Where is decay prevented, resulting in a fossil?

Ice in very cold regions and sap/amber

Why is decay prevented in sap?

There are anaerobic conditions

Why is decay prevented in ice?

Temperatures are too cold for Decomposers to operate

What are some examples of preserved traces, that count as fossils?

Footprints, burrows and rootlet traces

What is the name for fossilised faeces?

A coprolite

What is the cause (from animals) that the fossil record is incomplete?

Many early life forms were soft bodied - so they were completely eaten or totallly decayed

What are the environmental reasons that the fossil record is incomplete?

- Conditions needed to make fossils are rare

- many fossils have been destroyed by geological activity/ will never be discovered

Why may some fossils never be discovered?

They are too deep in the earth's crust

What can fossils tell us?

- Evolutionary relationships

- past climates

- how the earth's surface and organisms changed over long periods of time

- food source type

-sizes of past organisms

Why can scientists not be certain about how life began on Earth?

As the fossil record is incomplete

Which fossils do the oldest rocks hold?

The least complex organisms

Where are the oldest rocks?

bottom

Where can 2 organisms that lived in the same era be found?

In the same rock layer

How are rocks formed?

In layers

What is extinction?

The permanent loss of all members of a species.

What is constantly changing, that may lead to extinction?

The environment and therefore selection pressures

What stopes a species from n becoming extinct?

Evolution via natural selection - so the organisms become better adapted to their environments

What do all causes of extinction have in common?

A change ion the environment

Give the 5 main causes of extinction?

1. Single catastrophic event

2. New competition

3. New predators

4. New diseases

5. Environmental changes

Give an example of a single catastrophic event?

Natural disasters

Give an example of new competition?

Grey squirrels being introduced to england and OUTCOMPETING red squirrels

Give an example of new predators?

Hedgehogs being introduced as vermin control but instead eating the eggs of rare sea birds in a Scottish island

Give an example of new diseases?

The cancer causing virus for the Tasmanian devil

Give an example of environmental changes?

Global warming

What is classification?

The organisation of organisms into groups according to their similarities

Why is classification important?

There are millions of different organisms, so it allows us to make sense of the living world and how species are related to each other.

Who was Carl Linnaeus?

A scientist in Sweden during the 18th century

What did Carl Linnaeus develop?

The binomial classification system we use today

This system is phylogenetic - what does this term mean?

Based on evolutionary relationships

How many taxonomic ranks are there?

8

What is the way of learning the taxonomic ranks?

Domestic King Phil Cries Out For Green Shoes

What are the 8 taxonomic ranks?

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

What are the characteristics of the Linnaean system?

It is hierarchal and non overlapping

What does each species get in the Linnaean system?

A latin binomial name

What is the Latin binomial name made from?

The 1st word = genus (first letter capitalised)

The 2nd word = species

ALL ITALICISED OR UNDERLINES