Continuity of Life Flashcards
When was first form of life on earth?
3.5 billion years ago
What is the process of natural selection ?
forms of life having traits that better enable them to adapt to specific environmental pressures will tend to survive and reproduce in grater numbers than others of their kind thus ensuring the favourable traits in new generation
what are darwins theory to be necessary for natural selection ?
variation
birth rate
nature balance
what is variation ?
all membranes of a species shows some differences
What does birth rate have to be in order for natural selection to occur ?
always grater then the availability of resources would allow
What is nature balance in relation to natural selection?
despite high birth rate population members stay fairly constant
What was Darwin’s interpretations for natural selection?
struggle for survival
survival of the fittest
why does struggle for survival occur?
due to excessive birth rate and limited resources
what is the definition of survival of the fittest ?
because of variation within species those with the best suited characteristics have a higher survival rate more likely to pass on the favourable traits
What is Microevolution ?
changes of allele frequencies within a species or population over a short period of time
What is Macroevolution ?
major evolutionary change in regard to evolution of a taxonomic groups over a long period of time through the accumulation of microevolutionary changes
what does micro and macro evolution result in ?
changes in allele frequency in the gene pool of a population
how does variation occur?
through mutation
how is variation increased in a population?
sexual reproduction
what are the step of natural selection that lead to evolution?
- variation in a population
- more individuals produced than can be supported by an environment
- struggle for survival
- individuals with favourable genetic characteristics out-compete individuals lacking favourable traits
- favoured individuals survive
- Survivors have offspring
- desirable alleles passed on to offspring
- increase in favoured alleles in a gene pool
what are 3 selection pressures?
resource availability
Environmental conditions
biological factors
what are the types of natural selection ?
stabilising selection
directional selection
Disruptive selection
what is stabilising selection?
selection pressures are not changing optimal trait becomes more common
what is directional selection?
changing selection pressure leads to changing traits over time
what is disruptive selection?
favours extremes of phenotype ranges
what is the definition of speciation ?
the evolutionary process that leads to the formation of two or more new species from one original species
what is allopatric speciation?
occurs when two or more populations are prevented from breeding by geographical separation
what is gene flow ?
the movement of genes from one population to another through interbreeding which can introduces new genes into the population
what is the definition of species?
a group of organisms that are able to breed within the same species and successfully produce fertile offspring
what are the steps of speciation?
- variation
- isolation
- Selection
- reproductive isolation
what is variation in speciation?
all populations show different degrees of variation between individuals both phenotypically and genotypical
what is isolation in speciation ?
a population gets split into two by a geographical barrier and interbreeding between to population stop
what is selection pressure in speciation ?
different selection pressures favours different characteristics in each sub-population, gene pool changes independently of each other and gene flow stops. mutation can also arise resulting in more variation
what is reproductive isolation in speciation ?
the two populations accumulate enough genetic differences that interbreeding can no longer occur to produce fertile offspring.
what is the difference between speciation and evolution ?
- geographical barrier seperates population
- gene flow ceases
- different selection pressures in each population
- different mutations occur in each population
- each population evolves in isolation from the other
- too many difference have accumulated and are no longer the same species
what are gene pools and why are they studied ?
- The sum of the alleles in a given population.
- To observe how the characteristics in population are changing over time
what are the ways that genetic drift can occur?
- Random genetic drift
- The founder effect
- Bottleneck effect
what is random genetic drift ?
-when allele frequencies of a population change over generation due to chance event and not selection.
- occurs in all populations but effects smaller ones more
what is the founder effect ?
a small group of individuals that split off to start a new population, the founder population alleles may not represent the original populations alleles
what is the bottleneck effect
a sudden drastic drop in population size resulting in same alleles being lost
what is adaptive radiation ?
evolution of an animal or plant group into a wide variety of types adapt to specialised modes of life
what is the definition of fossil ?
preserved remains and traces of organisms over 10,000 years old
what are the types of fossils ?
- Trace - footprint, trail, burrow
- Mould - impression left by an organism
- Cast - formed when mould is filled with mineral rock
- Trueform - shells, teeth, bones
how do cast fossils form?
- animal dies its skeleton settles on the sea floor and is buried by sediment
- Sediment surrounding the skeleton thickens and begins to turn to stone.
- the skeleton is dissolved by groundwater and a mould is formed
- minerals from the groundwater crystallise inside the mould and a cast is formed
- the fossil is exposed on the earths surface by erosion
what conditions are required for fossilisation ?
- absence of decomposers
- absence of moisture
- low temperature
- high soil acidity
how does fossils provide evidence for evolution ?
- shows the change in structure over time
- shows how organisms have become more complex
- the variety of fossils increases the closer to surface
- no fossil record exist of any modern living plant or animal
- show the missing links between common ancestors
what is the principal of superposition ?
layers of rock at the top are younger then the ones beneath them
what are vestigial structure ?
a structure that during the course of evolution has been reduced in size or has lost its function
how does vestigial organs provide evidence for evolution?
show evidence of relationships among organisms
what characteristics do vertebrate embryos share?
- pharyngeal slits
- absence of pair appendages
- well developed post anal tail
- two chambered heart
- similar levels of brain development
how does comparative embryology provide evidence for evolution ?
- some vertebrates have traits as embryos that are not present in adults this is because ancestors use to have a use for the trait but no longer do
what are homologous structure ?
organs with similar structures but not necessarily similar functions.
how does homologous structure provide evidence for evolution ?
they suggest they all had a common ancestor with the same structure
what are analogous structures ?
organisms that are not closely related independently evolve similar traits as a result of having to adapt to similar environments
what is comparative genomics?
the study and comparison of the genome sequences of different species
what is comparative studies of DNA?
every organism uses the same DNA code they just have different sequences between each organisms. the longer that organisms have been separated the grater difference they have in there DNA
what is the process of DNA hybridisation ?
- DNA of two species extracted, cut into short fragments and denatured
- DNA are purified to leave a single stranded copies of only one side of the DNA
- DNA are then mixed and cooled to allow annealing (the more similar the DNA the more bases will match )
- these strands are then reheated to again denature them the bonging strength is measured by the heat required to separate them
how do you know if DNA hybridised DNA has strong bonds or not?
- the higher the temperature is to seperate the DNA the stronger the bonds
what is used to provide evidence for evolution when looking at comparative biochemistry ?
DNA sequencing
Mitochondrial DNA sequencing
Protein sequencing
Ribosomal DNA
what is comparative biochemistry is relation to evidence for evolution ?
Large amounts of genetic data is compared
The closer the sequence (DNA/RNA/Amino acid) the more closely related the organisms.
what is selective breeding ?
the selection by humans of animals or plants with desirable phenotypes for breeding to produce offspring with the desirable characteristics
what is a negative to selective breeding ?
it decreases the biodiversity of the species
it creates a smaller gene pool
what are some desirable traits that are used for selective breeding ?
disease resistance
faster growth rate
improve product quality
improved yield
Tolerance to adverse conditions
what is inbreeding depression ?
is the reduced biological fitness in a given population as a result of inbreeding
what is the process of artificial selection ?
- identify the desirable trait
- choose the parents with the desired trait
- the selected parents are then crossbred to produce offspring that inherit the desired trait
- the offspring are then evaluated and the individuals with the most desired traits are selected as parents for the next generation
- the process is repeated
what is the definition of extinction ?
the process of death of all the members of a population or species
what does biodiversity allow a population do?
genetic diversity allow a population to effectively evolve and adapt through natural selection
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.
what does biogeography have an effect on ?
environmental factor
human
how does biogeography maintain gene pools?
Conservation areas need to be large enough and have suitable conditions to maintain viable populations
Populations in different geographical locations will be genetically different due to different selection pressures
inbreeding depression
outbreeding depression
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.
how does reproductive behaviour maintain gene pools ?
-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
how does population dynamics in conservation maintain gene pools ?
-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
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 dynamics.
