Evolution Flashcards
(83 cards)
what is evolution?
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.
What does evolution theory try to explain?
The evolution theory tries to explain how all life on Earth came to exist.
What is evolution theory based on?
It is a theory based on evidence that is tentative and limited (incomplete).
What is the geologic time scale?
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.
define population (ecological)
a group of a particular species living in the same geographical area at the same time
define variation
genetic differences within a population
define adaption
characteristic that contributes to a species’ suitability for its environment
define species
two organisms belong to the same species if they can interbreed to produce fertile viable offspring
define traits
observable characteristics found in a species
define gene pool
the range of traits found within a species as determined by the genes found in their DNA
define evolution
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
what do the mechanisms of evolution do?
these processes changes the genetic make-up of a population in some way
what are the mechanisms of evolution?
- 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
what is mutation?
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
what is gene flow (migration)?
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.
what is genetic drift?
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.
what is natural selection?
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
what is sexual reproduction?
random combination of genes results in variation in species
what is biodivesity?
The variety of life on Earth. (the variety of species, ecosystems and genes that exist
in a particular area)
what is species diversity?
the number of different species within an ecosystem
what is genetic diversity?
the range of genetic variation within a species
Why is biodiversity important?
provides functioning ecosystems that supply oxygen, clean air and water, pollination of plants, pest control, wastewater treatment and many ecosystem services
define extinction
when all members of a species die out
why do species become extinct?
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