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Evolution Flashcards

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Biology 101 flashcards
1
Q

what is evolution?

A

A theory that states that organisms alive today have developed from common ancestors, becoming more complex through a process of gradual change over millions of years (and is still occurring today.) Evolution refers to the genetic changes in a
population over a very long period of time.

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2
Q

What does evolution theory try to explain?

A

The evolution theory tries to explain how all life on Earth came to exist.

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3
Q

What is evolution theory based on?

A

It is a theory based on evidence that is tentative and limited (incomplete).

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4
Q

What is the geologic time scale?

A

The geologic time scale divides up the history of the earth based on life-forms that have existed during specific times since the creation of the planet.

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5
Q

define population (ecological)

A

a group of a particular species living in the same geographical area at the same time

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6
Q

define variation

A

genetic differences within a population

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7
Q

define adaption

A

characteristic that contributes to a species’ suitability for its environment

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8
Q

define species

A

two organisms belong to the same species if they can interbreed to produce fertile viable offspring

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9
Q

define traits

A

observable characteristics found in a species

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10
Q

define gene pool

A

the range of traits found within a species as determined by the genes found in their DNA

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11
Q

define evolution

A

progressive changes in the gene pool of a species over a very long period of time and many generations which results in new species arising

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12
Q

what do the mechanisms of evolution do?

A

these processes changes the genetic make-up of a population in some way

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13
Q

what are the mechanisms of evolution?

A
  • mutation
  • gene flow
  • genetic drift
  • natural selection
  • sexual reproduction – including the processes of ‘crossing over’ in meiosis and the random combination of genetic information from two parents
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14
Q

what is mutation?

A

random changes to DNA in individuals that can be passed on, showing different traits (can positively or negatively impact the individual):
- mutations introduce variations in new alleles. If the mutation happens to be advantageous and occurs in the gametes, it may lead to a shift in the genetic composition in the population of a species

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15
Q

what is gene flow (migration)?

A

Interbreeding between different populations from movement of a population:
Gene flow specifically refers to the movement in genetic material the individuals carry from one population to another. However, gene flow can only occur between separate populations that are still part of the same species because they must be able to reproduce.

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16
Q

what is genetic drift?

A

Gradual changes to the features of a species: Genetic drift is the process by which the genetic information in a population changes at random or due to a chance
event, key in small populations
contains much less genetic diversity. In this way, genetic drift can cause a large loss of genetic variation in small populations. This loss of genetic variation may result in the new population becoming more genetically distinct from the original population.

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17
Q

what is natural selection?

A

environment determines the likelihood a trait is passed on to the next generation.
the process that when applied to a population results in the continued existence of only the organisms that are best suited to the conditions in which they live, those better suited will survive and are more likely to pass on their genetic information

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18
Q

what is sexual reproduction?

A

random combination of genes results in variation in species

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19
Q

what is biodivesity?

A

The variety of life on Earth. (the variety of species, ecosystems and genes that exist
in a particular area)

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20
Q

what is species diversity?

A

the number of different species within an ecosystem

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21
Q

what is genetic diversity?

A

the range of genetic variation within a species

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22
Q

Why is biodiversity important?

A

provides functioning ecosystems that supply oxygen, clean air and water, pollination of plants, pest control, wastewater treatment and many ecosystem services

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23
Q

define extinction

A

when all members of a species die out

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24
Q

why do species become extinct?

A

Species naturally go extinct over time due to numerous factors - although human action can accelerate this process

Mass extinctions have occurred in the past due to catastrophic events:
Asteroid impacts
Climate change
Volcanic activity
Sea level change
Glacial cycles

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25
Q

what is an endangered species?

A

a species that is in danger of becoming extinct

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26
Q

what is an adaptation?

A

A characteristic of an organism which increases its likelihood of survival in its environment

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27
Q

what process does adaption occur by?

A

natural selection

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28
Q

what are the three categories of adaptations?

A

structural, behavioural and physiological

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29
Q

what are structural adaptations?

A

Anatomical or morphological features of an organism.
Body coverings (fur, bright feathers, spines…)
Limb specialisations (webbed feet, opposable thumbs, wings, flippers…)
Sensory organs (eyes, ears….)

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30
Q

what are behavioural adaptations?

A

The things that an organism does which help them survive and thrive.
Communication
Social/territorial interactions (including conflict and cooperation)
Mating behaviours
Obtaining food
Maintaining homeostasis

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31
Q

what are physiological adaptations?

A

The way an organism responds on a cellular and molecular level.
Regulating body temperature
Water balance
Nutrient balance
Reproductive strategies
Senses and processing of sensory information

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32
Q

what are the three set of needs?

A

food/water/air
shelter/space/freedom from predators
access to mates (in order to pass on their genes)

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33
Q

what are evolutional adaptations?

A

the very slow very gradual changes in the POPULATION (not individual) over many generations that means that the individual animals and therefore the population can thrive in the place where they live

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34
Q

what is natural selection?

A

First proposed by Charles Darwin in ‘On the Origin of Species’ in 1859.
The main mechanism for evolutionary change. Proposes that organisms that are well adapted to their environment will more likely survive and thrive (produce more offspring) and pass on their genes, whereas those who are not adapted will die off. This process causes species to change and diverge over time.

35
Q

define selection pressures?

A

Selection pressures are external agents which affect an organism’s ability to survive in a given environment. They can be biotic (living) or abiotic (non-living)

36
Q

what are the different types of selection pressures?

A

Resources - Food availability (biotic), Shelter (abiotic), Availability of mates (biotic)
Physical environment - Temperature (abiotic), Weather (abiotic), Geography (abiotic)
Biological factors - Predators (biotic), Diseases (biotic)

37
Q

steps to explain natural selection?

A
  1. Variation exists in populations of organisms, requires differences to exist in the characteristics of individuals in a population. Differences largely arise through random mutations in genes.
  2. Specific animals have traits that make them well adapted to their environment (or more successful at meeting their three categories of needs). Some variations help organisms survive (they are selected for/have a selective advantage). Organisms with less favourable characteristics die out (selected against).
  3. Survival of the fittest - those that have the traits to make them more successful are more likely to survive, reproduce and increase those traits in the gene pool of the next generation.
    There is a struggle for survival referred to as ‘selective pressures’. Not all individuals in the population can survive.
  4. Over a LONG, LONG time the gene pool of the population will change, resulting in greater adaptation and the evolution of species.
    The organisms that survive pass on their traits to the following generations and over time the population changes to become better adapted to its environment.
38
Q

what happens if the environment changes in natural selection?

A

If the environment changes (e.g. a new predator arrives, climate change…), or if a population migrates to a new environment, then different characteristics may be selected for – and the population will evolve in a different direction.

39
Q

how did complex features develop through natural selection?

A

Most evolutionary change is slow and gradual.
Complex structures, like eyes and wings, evolved through small changes over many generations.
Existing structures were built upon over generations.
Each stage provided a survival advantage to that species.

40
Q

what is artificial selection?

A

Also known as selective breeding.

Artificial selection involves humans selecting individuals (plants or animals) that have the most desirable phenotypes, and exclusively breeding these individuals.

Over several generations, this process will change the population to become more suited to human needs/desires.

41
Q

difference between artificial selection and natural selection?

A

Artificial selection - humans select individuals with the most desirable phenotypes

Natural selection - nature selects individuals with the fittest phenotypes

42
Q

Issues related to artificial selection

A
  • Reduces genetic diversity - increasing susceptibility to disease
  • Often contradicts natural selection - creating individuals with health issues and unsuitable traits
43
Q

Benefits related to artificial selection

A
  • Artificial selection is certainly beneficial for humans who want plants and animals to show particular traits (such as better quality meat, wool, more aesthetic)
44
Q

what is included in the levels of classification?

A

All organisms can be uniquely identified using levels of classification.
As you move down the levels - each grouping contains fewer organisms, but the organisms become more similar and more closely related.

45
Q

how can you tell if organisms are of the same species?

A

Members of the same species are able to interbreed to produce viable and fertile offspring.

If the offspring of two organisms are not fertile (able to reproduce), then they are considered to be different species

46
Q

what is a subspecies?

A

Some species exhibit considerable variation across their range, and therefore groups in different regions are further classified as subspecies. (in time they may become separate species)

47
Q

what is speciation?

A

Speciation is the process where over time populations that are separated and experience different selective pressures, evolve (over many, many generations) to the point that they are no longer able to produce fertile offspring. The process by which new species are formed from an original ancestral species.

48
Q

define reproductively isolated

A

the inability of a species to breed successfully with related species due to geographical, behavioural, physiological, or genetic barriers or differences

49
Q

define viable

A

able to survive and reproduce

50
Q

define fertile

A

able to reproduce

51
Q

what are the stages of speciation?

A
  1. variation exist in the population/species
  2. Original population/species become geographically isolated into populations, cutting off migration between populations
    Physical barriers: River, Mountains, Continental drift, Rising sea levels, Climate change
  3. Different selection pressures act on the populations and favour those individuals with traits suited to each environment.
  4. Over a long period of time reproductive isolation occurs - even if the barriers are removed, individuals from different groups are unable to interbreed to produce viable/fertile offspring. They have become different species.
52
Q

what is evidence of evolution used for?

A

The evolution of life on this planet has already occurred. Therefore it cannot be directly observed.
Various forms of evidence can be used to conclude that all life is related and evolved from a common ancestor.

53
Q

what does fossilisation provide?

A

Fossilisaton provides a record of how creatures evolved and how this process can be represented by a ‘tree of life’, showing that all species are related to each other.

54
Q

examples of evidence of evolution

A

Palaeontology
Comparative anatomy
Comparative embryology
Molecular biology
Biogeography

55
Q

what is palaeontology?

A

The study of fossils.
Include:
direct evidence, such as fossilised bones, teeth and shells, indirect evidence, traces of fossils such as footprints

Provide evidence of the pre-existing life forms that lived on Earth. However the fossil record is largely incomplete.

56
Q

what are transitional fossils?

A

Fossils which are an intermediate between an ancestral species and a descendent species.
Help to establish an evolutionary relationship between species which appear very different to each other.

57
Q

what is fossilisation?

A

The process of a fossil forming.
Most commonly occurs when:
The organism is rapidly covered by oxygen poor sediment, meaning it is hidden from scavengers and decomposition is slowed.
Over a long period of time the sediment surrounding the fossil forms into sedimentary rock.

58
Q

what is relative dating?

A

Determining the order of age of fossils (without finding their precise age).
Stratigraphy, studying rock layers, allows us to determine the relative age of fossils
Deeper layers = older fossils

59
Q

what is absolute dating?

A

Provides a precise estimate of a fossil’s age.
Radioisotopes, such as carbon-14 (carbon dating) can be measured in a fossil sample. The relative amount of these isotopes in the fossils is used to determine its age.
if we measure the speed of breakdown of the isotope (called radioactive decay), we can work out how long an organism has been dead

60
Q

what is comparative anatomy?

A

Similarity in the structural features of organisms provides evidence of their evolutionary relationship

61
Q

what are analogous structures?

A

Structures that serve the same function in different organisms, but have evolved independently, eg;
Wings in birds, insects, bats, pterosaurs
Fins in fish and flipper in whales/dolphins

62
Q

what are homologous structures?

A

Structures in different species which are similar due to being inherited from a recent common ancestor.
Eg; although different mammalian species have highly modified forelimbs there are similarities in the bone structure.
These similarities suggest a common evolutionary ancestor for all mammals.

63
Q

what are vestigial structures?

A

Structures that no longer perform the same function as in other organisms.
These organs must have been important in some ancestral form, but became redundant in later species.

64
Q

what is comparative embryology?

A

Similarities in the developing embryos of different species.
Suggests a common evolutionary ancestor.

65
Q

what is biogeography?

A

The study of the geographical distribution of organisms.

66
Q

what is molecular biology?

A

Comparing the similarities in the molecules that make up organisms. Eg;
Genes (sequences of DNA bases)
Proteins (sequences of amino acids)
Haemoglobin
Cytochrome C
The more similar the molecules of two different species, the more closely related they are.

67
Q

what is DNA hybridisation?

A

DNA hybridisation is a technique to compare the DNA sequences of two species to find out how closely they are related.

68
Q

what is protein analysis?

A

a large difference in amino acid sequences between two organisms means they had a distant common ancestor, while a small difference in amino acid sequences mean they had a recent common ancestor

69
Q

what is evolutionary trees?

A

A visualisation of the relatedness of different species.
Each branch point represents a shared ancestor between groups of species.

70
Q

what is a fossil?

A

refers to any parts of, or impressions made by, a plant or animal that survives following death

71
Q

what are our common living ancestors?

A

Rather than evolving from chimpanzees, they are our closest living relatives
We share a common ancestor with the apes
Gorillas diverged from this common ancestor earlier than chimpanzees and bonobos did

72
Q

what are important structural features of humans?

A
  • Bipedalism (ability to walk on two legs)
  • Large and complex brain
73
Q

what are the advantages of bipedalism?

A
  • Energy-efficient form of movement
  • Helps avoid predators (standing taller enables you to see further), better gathering
  • Frees up the hands
  • Keeps the body cool with less direct surface area exposed to the sun and greater air flow in drier air to increase sweat evaporation.
74
Q

what are advantages and disadvantages of a large and complex brain?

A
  • Enables us to store more information
  • Enables us to collect and process information
  • Enables us to solve problems
    BUT
  • It is energy inefficient, and means we need larger skulls
  • Makes for difficult births
75
Q

skulls evolution?

A
  • Spinal cord enters human skull (through foramen magnum) from
    beneath
  • This means less energy is needed to balance the the head
  • Ape skulls attach from behind.
76
Q

mammal characteristics?

A

Warm blooded vertebrates, Give birth to live young

77
Q

primate characteristics?

A

Opposable thumb, Flattened nails (not claws), 3D colour vision, Relatively large brains

78
Q

hominoids (apes) characteristics?

A

No tail (unlike monkeys), Posture is partially or fully erect allowing hands to manipulate food, care for young or use tools, Larger body size and brain

79
Q

what were the adaptations for bipedalism?

A

Centering of hole in base of skull: Head is above centre of gravity - maintain balance

Reduction in relative arm length: Closer to centre of gravity

Femur: Longer and angled inwards from the hips. Positions upper body over the centre of gravity.

Shape of Foot: Platform shape (loss of opposable big toe)

80
Q

Selection for bipedalism

A
  • Carrying offspring.
  • Carrying food away from a kill site or growing site to a position of safety.
  • Efficient Locomotion:
    Bipedalism provides an energy efficient method that favours low speed, long distance movement – walking.
  • Seeing over the grass may have helped to spot predators at a distance.
  • Holding tools and weapons
81
Q

Selection for nakedness

A
  • Parasite control
  • Retention of head hair: Hair on the head reflects solar radiation (heat) before it reaches the skin.
  • Thermoregulation: Well developed sweat glands allow us to lose heat more efficiently.
82
Q

Trends in human evolution

A

Increasing height/body size
Increasing brain size and change in skull shape/structure to suit

83
Q

Evolution of the human skull

A
  • Increased cranial capacity (brain size) - Results in an increased cognitive capacity, and therefore problem solving skills and cultural behaviours.
  • Reduction in brow ridge
  • Facial angle sloped to vertical
  • Reduction in jaw size (skull becomes less about processing food, more about big brain storage)
  • Centring of hole in base of skull (assists bipedalism)

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