6.3 evolution and speciation Flashcards
(19 cards)
theory of evolution
all species of living things that exist today and many more that are now extinct have evolved from simple life-forms which first developed more than three billion years ago
what is evolution
a change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species
jean-Baptiste Lamarck theory of evoution
idea that changes that occur in an organism during its lifetime can be inherited—not true
charles darwin
had a five year expedition to the southern hemisphere on HMS Beagle
main observations:
characteristics are inherited from parents
more offspring are produced than the environment can support
this leads to competition between individuals for limited resources, e.g. food, habitats, mates
therefore not all individuals will survive to adulthood and reproduce themselves (most die, only the fittest survive)
natural selection
there is VARIATION in the population due to MUTATION
some individuals in the population have ADVANTAGEOUS ALLELES
These individuals are more likely to SURVIVE and REPRODUCE successfully. There is competition
These individuals pass on alleles over many GENERATIONS so ALLELE FREQUENCY INCREASES
why was Darwin’s theory of evolution only gradually accepted
the theory challenged the idea that God made all the animals and plants that live on Earth
there was insufficient evidence at the time the theory was published to convince many scientists
the mechanism of inheritance and variation was not known until 50 years after the theory was published (no knowledge of genes)
evidence for evolution
antibiotic resistance in bacteria:
variation in the resistance in bacterial population due to mutation
some bacteria have advantagrous alleles (resistance to antibiotics)
non-resistant bacteria are killed, resistant survive
less competition so resistant bacteria reproduce
genetic evidence: we have greater understanding of how characteristics can be passed on to offspring through genes
how to prevent new strains of antibiotic resistant bacteria appearing
only prescribe antibiotics for serious bacteria infections
take the full course of antibiotics if prescribed for bacterial infections
improve farming techniques so that farm animals don’t need to be routinely given antibiotics
fossils
the remains of organisms from millions of years ago that have been preserved in rock, ice or other substances
how are fossils formed
mineralisation:
organism dies and falls into water
soft parts are usually eaten or decay
hard parts remain (bone/teeth/shells)
over time layers of sediment build up
high pressure and a long time results in mineralisation (bones—>rock)
geological activity brings fossils near surface to be discovered
decay is prevented:
e.g. ice is too cold which prevents decay, amber prevents decay of insects by blocking oxygen
traces left behind:
imprints left in mud are mineralised after time
why is the fossil record incomplete
fossilisation is rare
many fossils remain undiscovered (e.g. under oceans)
many ancient organisms were soft bodied
extinction
the permanent loss of all the members of a species
causes of exinction
habitat loss
climate change
invasive species
new predator
hunting
aa single catastrophic event
intersprecific competition/better adapted cometition leads to lack of food
new disease
species definition
a group of similar organisms that can interbreed to produce fertile offspring
Alfred Russel Wallace
travelled the world gathering evidence to support his theory of evolution, focused on warning colouration in animals
published joint writings with darwin
speciation theory
- variation due to mutation
- geographical isolation
- habitat variation (different environment)
- natural selection occurs in both populations
- advantageous alleles are passed onto offspring
- No longer interbreed to produce fertile offspring
classification
the organisation of living things into groups according to their similarities
Carl Linnaeus classification system
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Don’t kill pets cos owners feel genuinely sad
binomial name: genus species
e.g. homo sapiens
homo = genus, sapiens = species
what can organisms now be classified based on?
evolutionary relationships
visible characteristics:
embryonic similarities (embryos)
genetic similarities
biochemical similarities
so additional level of classification developed by Carl Woese = domain
bacteria = true bacteria
archaea = primitive bacteria found in extreme environments
eukarya = animals, plants, protists and fungi
