Continuity Of Life Flashcards
1
Q
What are some key points of Earth’s Timeline?
A
- life has existed on Earth for approximately 3.5 billion years and has changed and diversified over time
- Earth formed 4.56 billion years ago
- First life (prokaryotes) 3.5 billion years ago
- Photosynthesising cyanobacteria 3 bya (produced oxygen)
- Multicellular organisms 2.1 bya
- Eukaryotes 0.6 bya (600 000 000)
- Marine animals
- Land plants 420 mya
- Land animals
- Homo sapiens 200 000 years ago
2
Q
What is mutation?
A
mutation is the ultimate source of genetic variation as it introduces new alleles into a population
3
Q
How does natural selection occur?
A
natural selection occurs when selection pressures in the environment confer a selective advantage on a specific phenotype to enhance its survival and reproduction; this results in changes in allele frequency in the gene pool of a population
4
Q
What is natural selection?
A
The process by which forms of life having traits that better enable them to adapt to specific environmental pressures (predators, change in climate, competition for food or mates etc) will tend to survive and reproduce in greater numbers than others of their kind thus ensuring the perpetuation of those favourable traits in succeeding generations.
5
Q
Darwin’s Theory of Natural Selection
A
Based on 3 observations
1. Variation- all members of a species show
variation
2. Birth Rate- is always far greater than
availability of resources (food etc) would
allow
3. Natures Balance- despite high birth rate
population numbers stay fairly constant
6
Q
Darwin’s Interpretations
A
Struggle for survival- due to excessive birth
rate and limited resources
2. Survival of the fittest- because there is
variation within the species, those with the
characteristics best suited to survival are the
ones that survive and reproduce and pass on
those characteristics
7
Q
What is Microevolution?
A
Microevolution- changes of allele frequencies within a species or population over a short period of time. Eg- bacteria
8
Q
What is Macroevolution
A
Macroevolution- major evolutionary change,
especially with regard to the evolution of whole
taxonomic groups over long periods of time
through the accumulation of microevolutionary
change. Eg. Evolution of horses
9
Q
What is evolution?
A
Evolution is change in the allele frequencies of
biological populations over successive
generations.
10
Q
What is speciation?
A
Speciation is the result of a population being split into two or more and evolving into different species
11
Q
How does variation occur?
A
Mutations
12
Q
How does variation increase in a population?
A
Sexual reproduction
13
Q
How does natural selection lead to evolution?
A
- variation in population
- more individuals produced than can be
supported by environment - struggle for survival (competition for resources)
- individuals with favourable genetic
characteristics out-compete individuals lacking
favourable characteristic - favoured individuals survive
- survivors have offspring (or produce more
offspring) - desirable alleles passed on to offspring
- increase in favoured allele in gene pool
14
Q
Adaptation over time
A
Environments change over time. Favourable characteristics therefore also change. This causes the gene pool to change and the population to evolve.
15
Q
What are selection pressures?
A
Any feature of the environment that reduces (or
increases) the fitness of a particular phenotype
in a population of organisms.
16
Q
Types of selection pressures:
A
Resource availability – Presence of sufficient food, habitat (shelter / territory) and mates
Environmental conditions – Temperature, weather conditions or geographical access
Biological factors – Predators and pathogens
(diseases)
17
Q
Types of natural selection
A
Stabilising Selection- when selection pressures are not changing optimal trait becomes more common
Directional Selection - changing selection pressure leads to changing traits over time
Disruptive Selection- favours extremes of phenotype range
18
Q
What is allopatric speciation?
A
Allopatric speciation occurs when two or more populations are prevented from breeding by geographical separation
19
Q
what is gene flow?
A
Is the movement of genes from one population to another, through interbreeding. Introduces new genes into a population. Makes populations more genetically similar
20
Q
What are some examples of geographical/physical barriers?
A
- Rivers
- Mountain ranges
- Oceans
- Lakes
- Canyons
- Deserts
- Roads
21
Q
What is a species?
A
A species is commonly defined as a group of organisms that are able to breed together to produce fertile offspring.
22
Q
Steps of allopatric speciation:
A
- Variation: All populations show different degrees of variation between individuals both phenotypically and genotypically
- Isolation: a population gets split into two by a geographic barrier. Interbreeding (gene flow) between the two populations stops.
- Selection: different selection pressures- natural selection favours different characteristics in each sub-population. Therefore gene pools change independently of eachother. Because there is no gene flow between the two populations mutations that arise in one population will not appear in the
other (= greater variation). The smaller the population the faster evolution occurs. - Reproductive Isolation: Eventually the two populations accumulate enough genetic differences that they can no longer interbreed, or produce fertile offspring (= different species).
23
Q
Key differences from evolution
A
- Geographical barrier separates populations
- Gene flow ceases
- Different selection pressures in each population
- Different mutations occur in each population
- Each population evolves in isolation from the other. Changes in the different gene pools
- Eventually the gene pools have accumulated so many
difference that they are no longer the same species
24
Q
What are gene pools?
A
The sum of the alleles in a given population. Geneticist study gene pools and allele frequencies to observe how the characteristics in populations are changing over time (microevolution). Alleles lost from the gene pool decrease biodiversity.
25
Why do allele frequencies change?
Mutation, Migration, Natural selection, Non-random mating, Genetic Drift
26
what are the three ways genetic drift can occur?
1. Random Genetic Drift
2. The founder effect
3. Bottleneck effect
27
what is random genetic drift?
Is a mechanism of evolution in which allele frequencies of a population change over generations due to chance events (eg death of an individual) not selection. Occurs in all populations, but its effects are strongest in small populations. May result in the loss of some alleles (including beneficial ones) and the fixation (100% frequency) of other alleles. The gene pool consists of all the alleles in all of
the individuals in a population. The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces. Over successive generations the gene pool may change.
28
what is the founder effect?
A small group of individuals splits off
to start a new population. More likely to be affected by genetic drift due to small population size. The alleles in the founder population may not be representative of the
original population. Once the population has increased the gene pool is still representative of the founder population not the original population.
29
what is the bottleneck effect?
A sudden drastic reduction in population size
- Drought, flood, fire, hunting, progressive environmental change. Surviving individuals constitute a random genetic sample of the original population (some alleles are lost). Small populations are more susceptible to genetic drift. Population numbers may recover but the gene pool will remain small. Populations with a small gene pool are more susceptible to changes in the environment and therefore have an increased risk of extinction.
30
What are fossils?
Preserved remains and traces of organisms
(over 10 000 years old).
31
Types of fossils:
- Trace - footprint, trail, burrow, coprolite
- Mould - impression left by an organism
- Cast - formed when mould is filled with
mineral rock (mineralisation)
- Trueform - shells, teeth, bones
32
How do cast fossils form?
There are several different ways fossils are formed.
1. An animal dies, its skeleton settles (organic matter
decomposes) on the sea floor and is buried by sediment.
2. The sediment surrounding the skeleton thickens and begins to
turn to stone.
3. The skeleton is dissolved by groundwater and a mould is
formed.
4. Minerals from the groundwater crystallise inside the mould
and a cast is formed.
5. The fossil is exposed on the Earth's surface by erosion
33
What conditions are required for fossilisation?
- Absence of decomposers
- Absence of O2
- Absence of moisture
- Low temperatures
- High soil acidity
34
How does the fossil record provide evidence for evolution?
1. Shows changes in structure over time
2. Organisms in the fossil record have become more complex over time. More recent (younger fossils) are more similar to organisms living today.
3. The variety of fossils increases in the upper more recent layers of rock
4. No fossil record exists of any modern living
plants or animals. This suggests that the organisms that are found as fossils either became extinct or evolved into species currently living.
5. Missing links - the common ancestor
35
what is the principle of superposition?
layers at the top are younger than the one
beneath them
36
what is correlation of rock strata?
- Matching layers of rock from different areas
- Rocks containing the same type of fossils (Index fossils) can be assumed to be the same
age
- Index Fossils- widely distributed, around only
for a limited time period
37
What can be told from studying the fossil record?
How long life has existed on Earth, how different plants and animals are related to
each other. Often we can work out how and where they lived from the other fossils found around them, and use this information to find out about ancient environments.
38
What are vestigial structures?
A structure that, during the course of evolution, has been reduced in size or has lost its function. Structure had a function in ancestors. Shows evidence of relationships among organisms (evolved from organisms where the structure had a function).
39
what are some characteristics that vertebrate embryos share?
* Pharyngeal slits (filter feeding ancestors)
* Absence of paired appendages (arms and legs)
* Well developed post anal tail
* Two chambered heart
* Similar levels of brain development
40
Explain comparative embryology:
Some vertebrates possess traits that are present in the embryos but are not present in adults. These traits had a function in the ancestors of the organism but not present in the adult because they do not have a function in the adult stage of these organisms. Suggests they all share a common ancestor. No other theory can adequately explain why the same structures occur in all chordate embryos when the adult forms are so diverse
41
what are homologous structures? (divergent evolution)
Evolution predicts that species coming from a common ancestor should share homologous characters; derived from the same structure(s) but that they will show divergence in these characters through time. Organs with similar structure but not necessarily similar function.
42
Example/s of homologous structures:
Pentadactyl limbs (5 digits), 2 bones in forearm
43
Evidence homologous structures provide for evolution:
Suggests they all had a common ancestor with that structure. The pentadactyl limb structure is not necessarily the best design for each of the varied modes of locomotion. Only organisms with the a common ancestor can have the
same basic structure (structures appear via mutation). No other theory can adequately explain why the same forelimb structure occurs in vertebrates with such diverse modes of locomotion.
44
What are analogous structures? (convergent evolution)
Process whereby organisms not closely related
independently evolve similar traits as a result of
having to adapt to similar environments or
ecological niches. Different structures with the same function. Evolved independently (different structure)
45
Example/s of analogous structures:
wing of bat, bird and insects
46
What is artificial selection (selective breeding)
The selection, by humans, of animals or plants with desirable phenotypes for breeding to produce offspring with desirable characteristics. Is a form of genetic engineering that has been going on for centuries. Causes changes in allele frequency of the gene pool. Results in decreased biodiversity and a smaller gene pool (inbreeding depression).
47
What is inbreeding depression?
Is the reduced biological fitness in a given population as a result of inbreeding, or breeding of related individuals.
48
What are some examples of desirable characteristics?
1. Disease resistance
2. Faster growth rate
3. Improved product quality
4. Improved yield
5. Tolerance to adverse conditions
49
Process of artificial selection:
1. Identify the desirable traits
2. Choose the parents with the desired traits
3. The selected parents are then crossbred to produce offspring that inherit the desirable traits.
4. The offspring are then evaluated, and the individuals with the most desirable traits are selected as parents for the next generation.
5. Repeat the process: The process of selecting and breeding the best offspring is repeated over several generations until the desired trait is consistently present in the population.
50
What is extinction?
The process of death of all the members of a population or species. May result in genes being permanently lost from the gene pool.
51
What are selection pressures?
Any feature of the environment that reduces the fitness of a particular phenotype in a population of organisms.
52
Examples of selection pressures?
- Competition for food, mates, space
- Predators, climate, food sources
53
What could happen if selection pressures are changed?
Changing selection pressures drive evolution but may also lead to extinction if populations don’t have time to evolve.
54
Examples of habitat destruction:
- Land clearing
– Agriculture
– Mining
– Housing
* Fires
55
Effects of climate change:
Global warming affects weather patterns
– Temperature, rainfall, sea levels, wind, ocean currents
* Plants in particular are affected as they cannot move away from adverse conditions
* Effects flow onto animals
56
Examples of introduced species:
- Predators
– Foxes
– Cane toads
– cats
* Competition
– Rabbits
– Prickly pear
* Disease
– Chytrid fungus
57
Examples of pollution:
- Air
– Particulates
– Photochemical smog from fossil fuels
* Land
– Dumping wastes, chemicals
* Water
– Fertilisers
– Crude oil
– Chemical residues
– Rivers, lakes, wetlands, coral reefs, ground water
58
Example of disease:
Facial tumours in Tasmanian Devil
59
what is the effect of humans?
Human activities have accelerated the rate of change in natural environments (global warming, land clearing, fire) to such an
extent that natural populations do not have time to adapt to the changes through natural selection.
60
what is comparative geonomics?
The study and comparison of the genome sequences of different species. Enables identification of genes that are conserved or
common among species, as well as genes that give each organism its unique characteristics. Has resulted in the redrawing of phylogenetic trees based on morphology.
61
What are the comparative studies of biochemistry?
- DNA
- Mitochondrial DNA
- Protein Sequences
- Ribosomal RNA
62
What are the comparative studies of DNA?
- All living things use the same DNA code (AT,CG)
* DNA sequence varies between organisms
* When speciation has first occurred the two new species would have very similar DNA
* The longer they have been separated the greater the differences in DNA
* Chimps share 98% DNA with humans
* Tested through DNA Hybridisation or DNA sequencing
63
Steps of DNA hybridisation:
1. DNA of two species extracted, cut into short fragments and denatured separately
2. DNAs are purified to leave single stranded copies of only one side of DNA
3. DNAs are then mixed and cooled to allow annealing (the more similar they are the more bases will match and the more strongly they bind)
4. These strands are then reheated to again denature them, the bonding strength is measured by the heat required to separate them
* Low temp=few bonds/high=many
64
What are endogenous retroviruses (ERV's)
ERV RNA enters cell and produces DNA (reverse transcription) that then inserts itself into a chromosome. If they enter chromosomes in the gametes then this is passed onto offspring. ERV’s make up 8% of human genome. Comparison of position and type of ERV’s indicates when different groups evolved.
65
What is DNA sequencing?
Modern technology allows the entire genome of an organism to be sequenced. The sequence of different species can be compared. The fewer differences the more recently they shared a common ancestor (more = more distant). Human DNA accumulates 100-200 new mutations (out of 3 000 000 000 bases) in every generation (20-30 years). The number of differences in the genomes can therefore be used to estimate the time since a common ancestor was shared by 2 species
66
explain phylogenetic trees
- A tree diagram representing the evolutionary relationship between organisms
- Branching of the tree represents the relationships between organisms
- The most recent descendent species are at
the tips of branches
- Common ancestors are at base of the tree
- Branching point represent time when each
branch last shared a common ancestor
- Branch length represents divergence time
- Closely related species will be grouped in
same part of tree
67
What is mitochondrial DNA (mtDNA)?
Inherited only from mother (sperm mito destroyed). mtDNA has a high rate of mutation (10x normal DNA). Slowly diverging from original female ancestor. Similarity in mtDNAindicates how closely related they are. Most useful for comparing individuals within a species or closely related species. Trace migration routes of hominin ancestors
68
what is ribosomal RNA?
rRNA inherited from mother. Highly conserved. Large changes would prevent ribosomes from
functioning
69
Explain protein sequences with examples:
10 000 proteins from 20 AA
* Greater difference in protein sequence = less closely
related
* Ubiquitous proteins
* Found in all species
* Perform basic but essential functions
* Cytochrome c (electron transport stage of cellular respirationeukaryotes)
* Slow rate of mutation
* Small – about 100 AAs
* Chimps and human identical
* and chains of haemoglobin
* Chimps and humans the same
* Gorillas 1 AA different
* Gibbons 3 AA different
70
what are bioinformatics?
The digital storage, retrieval, organisation and analysis of biological data (DNA sequences). Has increased the size, accuracy and scope of data sets such as those needed for comparative genomics. Used to compare DNA sequence in comparable structures in different organisms.
71
Uses of bioinformatics:
Bioinformatics- The science of collecting and analysing large sets of biological data using computer modelling.
* Construction, maintenance and use of databases to analyse biological data (AA sequences or nucleotide sequences)
* Compare DNA, genes and protein sequences within a species or between different species.
72
what is comparative biochemistry?
the study of evolutionary relationships between organisms based on differences in genomics.
73
what is comparative geonomics?
The study and comparison of the genome sequences of different species; comparative
genomics enables identification of genes that are conserved or common among species, as well as genes that give each organism its unique characteristics
74
what is resistance?
The ability of an organism to avoid or repel attack by biotic agents (pathogens, pests, parasites, etc.) or to withstand the effects of abiotic agents (chemicals, pesticides, etc)
75
what is immunity?
a complex biologicalsystem endowed with the capacity to recognize and tolerate whatever belongs to the self, and to recognize and
reject what is foreign (non-self).
76
evolution of resistance:
* Variation in the population
* Selection pressure (herbicide- roundup)
* Some individuals survive due to resistance to herbicide
* Survivors pass on resistance to offspring
* Farmers then need to increase the herbicide dose in order to kill the weeds,
repeating the process above and resulting in a population of weeds that are
resistant to even higher doses of herbicide
* This cycle continues until the herbicide is ineffective against the weeds
77
Why is it a superweed?
* Transgenes may enter genome from GMO crops providing a survival advantage
✓Pest resistance
✓Herbicide resistance
✓Lower water (or nutrients) requirement
* Factors limiting growth (water, pests) of transgenic plant are removed
* Therefore transgenic plant becomes difficult to control (a weed)
* May monopolise or deplete other resources (soil nutrients, water, sunlight,
space)
* Outcompete other plants (or change food web)
* Increasing survival
* Hard to control spread
78
What is biogeography?
the study of the geographic distribution
of living things and how those distributions relate to the environment, the origins of the species and the changes that have occurred over time.
* Biogeography’s main focus is on the effect of
1. environmental factors and
2. humans
on the distribution of a species
Knowledge of natural range allows biologists to
understand the variation in conditions that they can withstand and therefore their susceptibility to environmental change
79
what is inbreeding depression?
the reduction in fitness or the negative effects on the health and reproductive success of offspring that are produced by mating between closely related individuals.
80
what is outbreeding depression?
occurs when individuals from genetically
distinct populations are bred together and produce offspring that have reduced fitness or survival compared to their parents or the original populations.
81
Reproductive behaviours in conservation
* Behaviour associated with mating or rearing young
* Knowledge of reproductive behaviours allows biologists to recreate conditions conducive to reproduction in zoos
* Also allows biologists to ensure there are suitable reproductive conditions when reintroduced to the wild, eg nesting sites
* May change in captivity- could reduce the number of individuals that reproduce
* Reduces biodiversity in population
* High levels of inbreeding→ inbreeding depression
82
population dynamics in conversation
Understanding the conditions that will lead to an increase or decrease in the population allows biologists to intervene before populations begin to decline eg lack of nesting sites, drought
* Understanding the age structure of the population indicates potential to reproduce and therefore a population’s ability to recover from a change
* Small populations lack biodiversity- less resilient and stable
* Conservation planning should be based around smallest viable population size
* Can identify and potentially correct factors that cause numbers to drop
* eg if the majority of the population are very old they may be past breeding age and the population can decline very quickly
83
How and why populations change size
Births, deaths and migration
84
Minimum reserve size
Minimum size to maintain ecological processes is an important focus of conservation planning, and includes consideration of:
1. biogeography
2. reproductive behaviour
3. population dynamic
85
List the four factors (microevolutionary forces) of evolutionary change:
- Natural Selection
- Gene Flow
- Genetic Drift
- Mutation
