Chapter 9 - Where we fit in the world Flashcards
What is a species?
A group of similar organisms that have certain features in common
What are the features in common of a species?
Capable of interbreeding to produce fertile offspring
Biochemically and anatomically similar due to similar genes
How have new species developed?
Natural selection
What system is used to name organisms?
The binomial system
How are organisms written?
Genus species
e.g.: Homo sapiens
Italicised or underlined
Genus always begins with a capital letter
Why is the binomial system used?
It shows us whether organisms are closely related or not
What were old classification systems based on?
Observable features
What system do we use to classify organisms now?
Phylogenetic hierarchy
What does phylogenetic mean?
Organisms are placed in groups with other organisms that have close evolutionary relationships with them
What is the phylogenetic hierarchy?
Kingdom Phylum Class Order Family Genus Species
What happens as you go down the hierarchy?
Increasing similarity between organisms
What is the binomial name for humans?
Homo sapiens (wise man)
What happens as you go up the hierarchy?
Increasing number of species in each group
What are 5 kinds of evidence used in classification?
Biochemical Anatomical Embryological Immunological Behavioural
How are biochemical differences measured?
DNA hybridisation:
This involves taking two different unzipped strands of DNA and mixing them together
The more base pairings, detected by how much heat is needed to separate them, the more similar they are
What is the importance of the protein cytochrome c?
It has changed very little over millions of years and varies very little despite the huge range of Chordata it is found in
How is anatomy used in classification?
The more similar the anatomy, the more likely they are to be closely related
What does pentadactyl mean?
Five digits
Why are humans in the Primates order?
We have opposable thumbs Brachiation (180 arm swing) Large brains Stereoscopic vision Nails
How are embryos used to classify?
The more similar embryos look in early development, the more closely related they are
How is immunological evidence gathered?
Human serum is injected into a rabbit The rabbit makes anti human antibodies Serum is removed from rabbit Human and new rabbit serum is mixed A precipitate is formed from the antigen antibody complex
This can be used with other animal serum to see relationships
Behavioural evidence?
Helps to see how closely related they are by looking for similar behaviour
What did Lamarck propose?
The power to change was a natural property of an organism
What caused the need for change in Lamarck’s view?
The environment - the changes occurred because of an ‘inner need’
What did Lamarck say about the inheritance of these characteristics?
Characteristics acquired in their lifetime were passed on to their offspring
Where did Darwin get evidence for natural selection?
Galápagos Islands
What were Darwin’s two facts and the conclusion from this?
All organisms over-reproduce
But, organism numbers in species remain roughly stable as a result of competition for resources
He concluded that there is a struggle for existence
What was his third fact and what did he conclude from this?
There is variation between members of a species
Those with particular variations will be more suited to survive an reproduce
What is meant by natural selection?
Any variation may be an advantage or a hindrance in the ‘struggle for existence’
Those with favourable variations will survive, reproduce and pass on their successful alleles
Those without will not survive, therefore will not reproduce and pass on its alleles
Summarise industrial melanism
Pre-industry: speckled moth was only known species
Industry: 98% were melanic
This gave them an advantage as they could camouflage on tress covered in soot
These moths passed on their alleles
What is speciation?
The development of new species
How can speciation occur?
Geographical isolation:
- Different phenotypes are suited to different environments, so the different alleles will increase in frequency amongst themselves
- Successful alleles caused by a mutation will be passed on, and will increase in frequency in the population
- Genetic differences become so large that they can no longer interbreed to have fertile offspring - this is called reproductive isolation - so become different species
What did Darwin study to show speciation?
Finches on different Galápagos Islands
What are fossils?
Preserved remains from a living organism
How can fossils be preserved?
In ice, amber, rocks, or bogs
What else can fossils be?
Imprints
Why is fossilisation rare?
The dead organism is usually eaten by a scavenger
What are the two methods of dating fossils?
Carbon dating
Potassium-argon dating
How does carbon dating work?
14C is present in CO2 in air
Therefore is eaten by animals via plants as they breathe it in
When animals die, no more 14C is incorporated
The half life of 14C to 12C is 5700 years
This can be used to date fairly recent fossils
What is potassium-argon dating?
40K decays into 40Ar
The half life of 40K is 1.25bn years
This can be used to see how old a fossil is by stratigraphy
What is stratigraphy?
The study of layers in rock - new rock generally forms over old rock
What can skew stratigraphy?
Natural occurrences such as earthquakes, volcanic eruptions and fault lines can split/ bend/ tilt the rocks so they are not in chronological order, or by weathering and heavy rain
What is a hominid?
An organism in the family Hominidae
What animals are hominids?
Humans, and great apes
When did humans and apes common ancestor live approximately?
5-7mya
What were the most important changes that happened as humans evolved?
An increase in brain size
Bipedalism
What is ‘knuckle-walking’?
A style of movement using four limbs
What 4 pieces of evidence prove bipedalism?
Foramen magnum position Pelvis shape Femur / knee position Foot shape Vertebral column
What is the foramen magnum?
The hole in the skull where the backbone meets with the skull
Where is the foramen magnum in humans and how does this affect neck muscle?
At the bottom of the skull
The neck muscles are small and low down as the head is balanced on the backbone
Where is a gorilla’s foramen magnum and how does this affect muscle?
At the back
Neck muscles are large and are high up
Describe the human’s pelvis
Short and broad; basin shaped
How does the human’s pelvis shape show bipedalism?
Organs are supported immediately above them
Describe the gorilla’s pelvis
Long and narrow
Describe the human femur and how the location of the knees is advantageous
Straight and has a long neck to fit into the pelvis
Knees are directly under the the pelvis and they lock when leg is straight
This allows humans to stand for a long time without using much energy
Describe gorilla’s legs
They cannot straighten them
Knees bend outwards from the pelvis
Describe the human foot
Arched
Big toe is parallel with the others
Therefore the foot is adapted for walking
Describe gorilla’s feet
Flat footed with an opposable big toe adapted for grasping
Describe human’s vertebral column and how this proves bipedalism
2 slight curves to make an S shape
The head is directly above the centre of gravity
Describe the gorilla’s vertebral column
Arched
Supports the weight of the body whilst knuckle walking
How can we tell the size of the brain?
By pouring sand into the foramen magnum until it is full
It is then poured out into a measuring cylinder to find the volume; cranial capacity
Where and when did Australopithecines evolve?
Africa
About 5mya
Describe an australopithecine
Ape like head; flat face, flat nose, no chin, powerful jaws, walked upright but had a rolling gait
Lucy is a fossil of what Australopithecine species?
A. afarensis
When did A. afarensis live?
4-2.5mya
Explain how A. afarensis lived
In family groups
Ate mainly plant food
They had long arms and ape like wrists
