Evolution Flashcards
Define evolution
A process by which new types of organisms develop from other existing types of organisms
Give some examples of evolution
- Amphibians evolved from fish
- Reptiles evolved from amphibians
- Birds and mammals evolved separately from reptiles
Explain how the scientific method works
- Scientists form a hypothesis for the question
- The hypothesis is tested
- Scientists test the same hypothesis in different ways - if it is upheld for most of the test, it becomes a theory
What are the main sources of evolutionary evidence?
- The fossil record
- Modification by descent and structural similarities
- Genetic similarities
- Biogeography
- Other (such as chemical evidence from proteins)
What is a fossil?
The preserved mineralised remains of living organisms found in rock
How are geologists able to date fossils?
They look at the chemical elements that the rocks contain. By dating the rocks, they are dating the fossils
What kind of rock are fossils found in?
Sedimentary rock (rock formed from layers of water-borne sediments)
What is the study of plant and animal fossils?
Palaeontology
How do fossils suggest that evolution has taken place?
They bear little resemblance to organisms living today indicating that species have evolved over time
When did life begin on Earth as a single-cell bacteria?
3.6 billion years ago (according to the fossil record)
What two things can fossils suggest about the earth millions of years ago?
The climate and environment
For example:
Fish fossils founds on mountains indicate that the area was covered by water in the past
What does the fossil record show us about organisms?
- How organisms have changed and developed over time
- Scientists look for differences in the ___ of body structures:
- Type
- Origin
- Function
What is the difference between extinct and extant?
Extinct - fossil species
Extant - still alive today
What is convergent evolution?
- When body structures are analogous
- Same function, different origin
- Slightly different structure
Give some examples of convergent evolution
- Wings on:
- butterflies
- bats
- birds
- All three wing types serve the same function but each evolved independently of each other
- Have a slightly different structure
When does convergent evolution take place?
When organisms not closely related living in different ecosystems evolve similar structures or features
What is divergent evolution?
- When body structures are shared by related species
- Involves homologous structures
- These body structures were inherited from a common ancestor
- This is called modification by descent
Name some examples of divergent evolution
- Bones in the forelimbs of a _____ are similar:
- cat
- frog
- bird
- lizard
- human
- All have:
- humerus
- carpal
- radius
- ulna
- Indicates a common ancestor
What can result from divergent evolution?
- Vestigial Structures
- Small and poorly-developed
- no useful function today
- inherited from an ancestor
Give TWO examples of vestigial structures
- Whales and some snakes that have pelvises and undeveloped hind leg bones though they have no hind limbs
- The human appendix
What can modification of body plans refer to?
Either divergent or convergent evolution
How is the embryo evidence for evolution?
- Similarities can be seen in the embryos
During early embryonic stages of development, what do all vertebrate embryos have?
- A nerve cord which becomes a spinal cord
- A supporting rod (notochord) which becomes a vertebral column
- Gill slits
- Fish-like heart
- Fish-like kidney
During the early stages of development of certain vertebrate embryos, which animals can one not tell the difference between?
- A fish
- A frog
- A chick
- A pig
- A human
What can divergent evolution also be known as?
Modification by descent
What does DNA code for?
The formation of protein molecules
What does DNA make up?
The genes that parents pass on to their offspring
How can we use DNA to show evolutionary relationships between different groups of organisms
By comparing similarities and differences between the DNA
Studies on _____ show show similaries in cell chemistry in a wide range of organisms
Cell proteins and nucleic acids
What indicates that DNA was inherited from common ancestors?
Close similarities in the DNA of different species
What occurs as a result of genetic similarities
Chemical similarities
Remember: DNA determines the chemical make-up of organisms
If organisms share certain chemical features, then…?
The organisms are related and the chemical features were inherited from a common ancestor
Give an example in two groups of organisms (great apes and humans) that share similar chemical features
- The specific proteins that are needed for human colour vision are exactly the same as those found in the great apes and monkeys that live in Africa and Asia.
This suggests that these species all evolved from a common ancestor.
A protein called _______ can be used as evidence for evolution in what way?
- Cytochrome C
- Organisms with identical Cytochrome C amino acids in the protein:
- bacteria
- fungi
- tuna fish
- silkworms
- frogs
- humans
- Which two animals have identical Cytochrome C proteins?
- Which animal differs from this by only one amino acid?
- Humans and Chimpanzees
- Rhesus monkey
Which protein besides Cytochrome C and the protein needed for human colour vision has also been studied as evidence for evolution?
Haemoglobin
Define biogeography
The study of the distribution of species
Give TWO examples of species whose biogeography supports evolution
- Most Marsupials live in Australia
- Six species of baobab in Magagascar and only one in Africa and one in Australia
- Madagascar is the centre of baobab evolution
Who was Lamarckism founded by? When was this person alive?
Jean-Baptiste Chevalier de Lamarck (1744 - 1829)
What are two GENERAL characteristics about Lamarck?
- He was the first evolutionist to publicly state his ideas on evolution
- His ideas were wrong
What did Lamarck believe that evolution was mainly due to?
Acquired characteristics being inherited as creatures adapt to their environment
Give an example of an explanation of evolution in terms of Lamarckism
Giraffes evolved long necks because each generation stretched further to access high leaves in the trees and that this change in body shape was inherited by the next generation.
Along with the inheritance of acquired characteristics, what else did Lamarck believe?
He thought orgnaisms could develop new organs or change existing ones depending on whether they were used or not
What one thing was Lamarck right about in terms of how evolution is driven?
The environment is important in causing changes in organisms
What theory did Darwin introduce?
The theory of evolution by natural selection
Explain how Darwinism says that natural selection could result in a new species
- Organisms compete for resources (food, water, space)
- Any variation within an organism that favours survival in a particular environment would increase its chances of reproducing
- Organisms with less favourable characteristics are less likely to reproduce
- More favourable variations are passed on to future generations
- As number of variations increases, a new species could results
What is the opposite of punctuated equilibrium? Explain this concept.
- Gradualism
- This is the former theory that evolution occurred gradually and slowly over time
Explain the concept of puntuated equilibrium
- Gaps in the fossil record indicated that evolution was not a gradual process
- Evolution occurs in sudden bursts after long periods of no change
- Occurs in big jumps rather than in small steps
- Climate changes which happen every few thousand years, can play a part in this.
- Species that cannot adapt to the changes fast enough become extinct
- Species that adapt to the changes evolve
Who proposed the theory of evolution by punctuated equilibrium and when?
Niles Eldrege and Stephen Jay Gould in 1972
Give another term for artificial selection
Selective breeding
How do humans act as an agent for evolution?
- Through artificial selction
- Animal breeders change the characteristics of animals by breeding animals that have the desired qualities
- racehorses
- cows
- pigs
- chickens
What characteristics have crop species been artificially selected for?
- fragrance
- drought resistance
- yield
Our major crop plants have been…
Artificially selected from their wild ancestors
What kind of plant does the maize that we eat today come from? Where is this plant originally found?
- Teosinte plant
- Indigenous to Mexico
What is the difference between the ancestor of and the maize that we eat today?
How was maize developed by artificial selection?
- There are variations in the population
- The plump seeds are collected and planted
- These plants carry more alleles for plumper kernels.
- Seeds from plumpest of these are collected.
- These carry even more alleles for plump seeds and eventually the frequency of the allele for the characteristic that you want increases
What are some disadvantages of artificial selection?
- Removes a lot of variation in the population
- Prone to diseases
- Changes in environment could be problematic
- The whole of an artificially selected species (such as maize) could get a disease and become extinct
Explain the process of evolution by natural selection
- Variations are present in a population
- Passed from parents to offspring
- Variations that favours survival of an organism would increase its chance of successfully reproducting and passing on its genes
- In time, these individuals will outnumber individuals of the same species with less favourable variations
- Over time, as the number of individuals with favourable vatiations increases, a new species could result
What are variations?
Variations are the result of small changes in the genetic make-up of individuals of the same species.
What are variations the result of?
- Mutations
- Sexual reproduction (crossing over during meiosis)
The bigger the gene pool, the …
more variations (genetic differences) in a species
Give some examples of certain favourable variations
- Variations enabling an organism to:
- Resist disease
- Outrun predators
- Survive unfavourable environmental conditions (drought or climate change)
Which process drives evolution?
Natural Selection
Nature selects individuals with favourable variations by eliminating those with unfavouable variations.
Define an adaptation
Any change in the structure or function of an organism that allows it to live successfully in an environment
What are traits that have been selected by natural selection?
Adaptations
Do adaptations develop because of the environment?
No.
It is organisms that have favourable traits that survive and pass this variation onto their offspring. The organisms with unfavourable traits die.
What is selection pressure?
When environmental factors determine whether an organism has suitable variations to survive or not
What is continuous variation?
Continuous variation shows a characteristic of any species that changes gradually over a range of values
Give some examples of characteristics in humans which are typical of continuous variation
- Height
- Weight
- Foot length
What is discontinuous variation?
A characteristic of any species with a limited number of possible values
Give some examples of discontinuous variation
- Gender
- Blood Group
- Eye Colour
Define a species
A group of organisms that are able to reproduce and produce fertile offspring
Do organisms have a look similar to be a species?
No.
They are a species as long as the are able to reproduce
Can you apply the species concept to organisms that reproduce asexually?
It is difficult to do this.
Define speciation
The process by which new species form
All evolutionary changes in species are due to _____
Genetic changes (changes in an organism’s DNA)
In any population, there are several _____ that code for a particular characteristic.
Alleles
What is the frequency of different alleles in a population defined as?
The proportion of a particular allele of a gene relative to the other alleles of the same gene
What does the frequency of all the different alleles added together in a population equal?
1
What happens when the frequency of certain alleles in a population changes over time?
A new species forms
What is it called when two genetically different parents mate? What kind of organism do they form?
Hybridisation forming a hybrid organism
Is a hybrid organism a different species to its parents?
Yes. It is classified as a new species
Is hybridisation more common in plants or in animals?
Hybridisation is more common in plants than in animals.
Give an example the process of one hybridised plant species forming.
Peppermint
Watermint x Spearmint
In South Africa, people are most concerned about the hybridisation of the _____ species. This happens when…
- Hybridisation of antelope species
- Occurs when species are introduced into areas that are outside their natural ranges
Give some examples of animals in South Africa that are commonly hybridised
- Blue Wildebeest x Black Wildebeest
- Burchell’s zebra x Hartmann’s zebra
- Bontebok x Blesbok
- Red hartebeest x Tsessebe
What is the main cause for speciation?
Geographic Isolation
What factors causes speciation to occur most of the time?
When populations are physically or geographically separated from one another.
What differs slightly in two isolated habitats?
Ecological (environmental) conditions
What two things, most of the time, isolates two populations from each other?
- A mountain
- The sea
What happens to isolated populations under different environmental conditions?
The two populations evolve
Give some examples of characteristics that change by natural selection over many generations
- Body Shape
- Food preferences
- Reproductive patterns
How are new alleles formed in a population?
Over multiple generations, random mutations take place
Geographic isolation can change the _______ in populations leading to the formation of a new species
Frequency of alleles
What would happen if the barrier separating two species were to suddenly disappear
They would not be able to reproduce anymore - two new species would have formed
Explain how geographic isolation leads to speciation
- Populations are physically or geographically separated from one another
- Each of the isolated populations evolves under the different environmental conditions
- Random mutations take place leading to the formation of new alleles
- The fequency of alleles in the populations changes (This means two new species have formed)
What was the ship that Darwin travelled on?
Beagle
Where did Darwin travel to on Beagle?
He visited the Galapagos Islands off the coast of Ecuador in South America
What was common between the 13 species of Darwin’s finches?
They all had a common ancestor
Name the different kinds of finches that evolved
- Ground finches (find food on ground or shrubs)
- Tree finches (feed on insects)
- Finches with stout beacks (eat seeds)
- Finches adapted to eating insects or nectar
- Beak like a woodpecker (uses cactus pine to dig out insects)
- Finches that looks more like a warbler
What kind of breeding environment did the finches have on the Galapagos Islands?
- No predators
- No competetors
What else, besides Geographic Isolation, can cause speciation?
Reproductive isolation
Define reproductive isolation
Reproductive isolation is a means of stoppping two or more populations from exchanging genes during reproduction
Name SIX ways in which reproductive isolation can occur
- Temporal isolation
- Behavioural isolation
- Mechanical isolation
- Ecological isolation
- Gametic isolation
- Sterile or infertile offspring
Does evolution have to take millions of year to occur?
No. It can happen very quickly
In which types of organisms does evolution occur the quickest?
Organisms with very short life cycles such as:
- Bacteria
- Insects
- Viruses
What does DDT stand for
dichlorodiphenyltrichloroethane
How have mosquitos developed resistance to DDT?
- A few are resistant to DDT
- These mosquitos survive
- A whole new population of DDT resistant mosquitos develops
- The allele that breaks down DDT is now established in the population
Why has DDT been banned in most countries?
- It accululates in the tissues of organisms
- Causes extensive harm to animals further up food chains (including humans)
What is a pathogenic organism?
A disease-causing organism
What can happen when doctors prescribe drugs to get rid of pathogenic organisms?
The pathogenic organisms become resistant to drugs and undergo evolution by natural selection in a very short time.
The bacteria causing _____ keeps evolving resistance to the antibiotics used to treat the disease. What needs to be done about this?
TB
New drugs needs to be generated all the time to be effective against the new anti-biotic resistant bacteria
What is HIV?
A virus
HIV drug resistance occurs in the same way as…
Drug resistance in bacteria
Most HI viruses will be destroyed by anti-retroviral drugs but some have…
Genes that make them resistant to the drugs (which thus allow them to survive)
What happens to the HIV that survive the anti-retrovirals?
The replicate to form new, drug-resistant populations of HIV.
Which seeds (large or small) are more abundant in wet years
Small seeds are abundant in wet years
Larger (and tougher) seeds are more abundant in drought years
What is the changes in bill sizes according to wet or dry years an example of?
Fast evolution through natural selection
What is the study of human evolution using fossils and artefacts?
Paleoanthropology
What are artefacts
Objects such as tools and jewllery
What does it mean if a number of species share many features?
They are related by descent from a common ancestor
What kind of evolution is modification by descent from a common ancestor?
Divergent evolution
What explains why all vertebrates have the same bones in their forelimbs and why all orchid flowers have the same basic structure?
Theory of common descent
Why did Darwin say that Africa is the most likely place to find the ancestor of humans?
It is where the great apes (the species most similar to us) live.
What is an alternative explanation to evolution?
Creationism
What are humans classified in?
The Order Primates
How many living species do the Order Primates consist of?
200 living species including:
- monkeys
- baboons
- apes
The apes are a group of primates including…
- Gibbons
- Orangutans
- Gorillas
- Chimpanzees
How long ago did the common ancestor that all primates evolved from live?
- About 30 million years ago
- You can refer to the phylogenetic tree on page 242
What shows that humans are related to apes and that their closest living relatives are chimpanzees?
DNA testing
Did humans come from chimpanzees?
No. Chimpanzees and humans both evolved from a common ancestor
Name three kinds of evidence for human evolution (evolution of living homonids from a common ancestor)
- Fossil evidence
- Cultural evidence
- Genetic evidence
Was the common ancestor of chimpanzees more like an ape or more like a human?
More like an ape
What characteristics do the fossils that fit between the common ancestor and modern humans have?
- Skeletons adapted for bepedalism
- Larger brain size
- Smaller face
- Smaller teeth
Who found the first fossil which filled the gap between the common ancestor and humans? When and where did he find it?
Professor Raymond Dart in 1925 at Taung (in South Africa)
Who found another fossil, after Raymond Dart, that also filled the gap between the common ancestor and humans? Where did he find it and when?
Dr Robert Broon at the Sterkfontein Caves (near Johannesburg) in 1945
Where else, after 1945, have many fossil fragments been found?
South Africa and East Africa
What can be used to compare the anatomy of two closely related species?
Fossils
What is a phylogenetic tree?
A diagram showing the relationship between fossils
What does the word “homonids” refer to?
Humans and their fossil ancestors
How many species of homonids lived in the past 6 million years?
18 species
What part of a cell has its own DNA?
Mitochondria
What happens at fertilisation to the sperm’s mtDNA and the egg’s mtDNA?
The sperm’s mitochondria stays outside the eff so only the mother’s mtDNA is passed onto the offspring
What can happen each time mtDNA is copied?
A mutation can occur
What can be noted about the number of mutations of mtDNA occuring?
The number of mtDNA mutations occuring continues at a steady rate
How can mutations of mtDNA spread?
Within isolated populations, but not between populations
What does the number of differences in the mtDNA of two species tell scientists?
How long ago the species separated.
What can be noted about the mtDNA if the species separated recently?
- If the species separated recently, there are few differences
- If the species separated long ago, there are many differences
What is a cladogram?
A diagram comparing and showing the relationship between mtDNA.
What can confirm that the common ancestor for all apes and human lived about 15 MYA?
A cladogram
Cultural evicence of human evolution comes from studying…
Fragments such as:
- Sticks
- Burned bones
- Stone implements
- Pottery
- Jewellery
- Artwork
What are THREE key adaptations that enabled Homo to become expert at working with hands?
- Bipedalism
- Opposable thumb
- Broader, more sensitive fingers
Which THREE features of the skeleton does the ape have which the human does not have?
Brow ridge
Forelimb
Hindlimb
What are classified as homonids?
Humans and their anestor
(Including the extinct upright apes)
Give FOUR characteristics of homonids
- Bipedalism
- Modification of hands
- Skull (Also, brain size and dentition)
- Language
Define bipedalism
Walking on two legs
Name SEVEN aspects that needed to be modified to allow for bipedalism
- Foot bone arrangement and size
- Pelvis size and shape
- Knee size and angle
- Leg length and angle
- Vertebral column shape and orientation
- Cranium shape
- Shoulder blades (Scapulas)
How must the foot bones be arranged to allow for bipedalism?
- The big toe must be aligned with other toes
- Other primates have an opposable big toe
How must the pelvis be shaped to allow for bipedalism?
The pelvis must be:
- Larger
- Shorter
- Broader
This allows it to support the greater amount of body weight passing through it.
What characteristics must the knee have to allow for bipedalism?
The knee joints must be:
- Enlarged
- Angled inwards
This allows them to bear increased weight
What characteristics must the leg have to allow for bipedalism?
- The femur ball must be:
- angled inwards towards pelvis socket
- strenthened
- Increase in leg length
- changes how muscles work
- allows humans to use natural swing of leg
How must the vertebral column change to allow for bipedalism?
The spinal column must change from straight to S-Shaped.
This gives it flexiblility.
How must the skull change to allow for bipedalism?
Foramen magnum shifted forward:
- Allows skull to balance on spine
- Allows eyes to look forward
How must the scapula change to allow for bipedalism?
Must become:
- Wider
- Straighter
This alllows for better upright posture
Why is bipedalism important?
- Frees hands for carrying things
- Improves vision
- Reduces body area exposed to sun
- Makes it easier for hunting and fighting
- Makes it easier to feed from bushes and low branches
- The increased height intimidates predators
- It is easier to carry offspring
- More energy-efficient way of moving (than swinging through trees)
Hands have evolved to make the following movements:
- Spreading fingers apart
- Cupping the hands
- Wrapping fingers around objects
- Opposable movement
The change in hand bones gave homonids…
- The precision grip
- The power grip
What did the precision grip and power grip allow for?
Unique cultural developments:
- Tool making
- Using tools
- Painting
How did language come about?
- Skull enlarged (facial bones - smaller; lower jaw - shorter)
- This made more space for larynx movement
- Vocalisation developed (which then led to language)
State the OOA (Out Of Africa) Hypothesis
Homo sapiens first evolved in Africa (in Ethiopia or Sudan) and migrated from there round the world
How long ago did humans migrate into North Africa?
160 000 years ago
How long ago did humans migrate into South Africa?
120 000 years ago
How long ago did humans cross into the Middle East?
100 000 years ago
When did the second migration occur? What happened then?
85 000 years ago
Homo sapiens crossed into the Arabian Peninsula and from there migrated to China
Why did humans migrate?
- Humans followed migrating herds which was their food supply
- Competition for resources (space, food and shelter) could have forced the migration
Where were the oldest known fossils of the genus homo been found?
Africa
Transitional fossils between which two species are found only in Africa?
Transitional fossils that show intermediate stages between H. ergaster and H. sapiens are found only in Africa
What kind of evidence most strongly suppports the OOA hypothesis?
Genetic evidence
What confirms that all modern humans are descended from a single population of H. sapiens that probably lived in Ethiopia or Sudan?
DNA analysis
All modern humans are…
Very similar
What indicates that all humans evolved from a single region in Africa?
Comparisons of:
- Modern human chromosomes
- Nuclear DNA
- mtDNA
What shows that African people are the most ancient on Earth?
The cladogram
because African people have the most mtDNA mutations
What forms between continental plates that are moving apart?
A rift valley
What has exposed many of the hominid fossil sites?
The East African Rift Valley as it has grown deeper and wider over millions of years.
Label the skeleton of Ardepithecus in terms of ape-like and human-like features
Label the skeleton of Australopithecus in terms of ape-like and human-like features
Label the skeleton of Homo in terms of ape-like and human-like features
Compare the differences (tabulated) in anatomy of chimpanzees and humans
Tabulate FOUR differences between the skull and pelvis of the primates
Give reasons for the difference in the positions of the foramen magnum of the human and chimpanzee skulls
- Indicate differences in modes of locomotion
- Human
- centrally located
- allows for bipedalism (so that eyes look forward)
- Chimpanzee
- located at back of skull
- spine exits at an angle
Foramen magnum of Australopithecus is further forward than chimpanzee. Not as far forward as H. sapiens.
Why did Prof. Dart say that the Taung skull was intermediate between the common ancestor and humans?
- Foramen magnum was further forward than in chimpanzees
- Teeth were smaller than a chimpanzee’s
- Palate was broader than a chimpanzee’s palate
- Canines were smaller
- No gap between incisors and canines
- All these features were between chimpanzees and humans
TABULATE the differences between the three phases of human evolution.
Include:
- Age
- Adaptation to bepedalism
- How did it move
- Skull features
