Topic 5: Evolution Flashcards
evolution defintion
a change in the heritable characteristics of a population over time
evolution evidence from fossils `
-in the 19th century, studies of rock layers revealed a differences in the fossils contained in each layer.
-plant fossils begin before animal fossils, plant on land appears before animals on land.
-plant suitable for insect pollination appear before insect pollinators.
homologous structures
-have a fundamental similiarity of strucutre by are adapted to different function.
homologous structures suggest a common ancestor, shared by a range of diverse organisms.
related organisms show a wide diversity of a basic structure.
Analogous strucutre
-have no structural similarity but have similar function.
analogous structures are not based on shared ancestry.
-unrelated organisms experience the same selection pressure and gradually evolve to be better suited to that environment.
evidence from homologous strucutres
the pentadactyl limb has a single evolutionary origin, and has become different over time as it performs different functions in different species.
Speciation
due to divergence of isolated populations can be gradual or it can occur abruptly (punctuation equilibrium)
Process of speciation
- Isolation of population
- Isolated populations will experience different selection pressures due to natural selection. Genetic divergence occurs.
- Divergence into different species occurs when the trairs that evolved over time prevent indidvudals from the seperate populations interbreeding. At this point the populations are considered to be seperate species.
Industrial melanisms
melanistics varieties of specices tend to become more frequent, in populations located in polluted indurstrial areas where their darker colouring makes them better camouflaged than the lighter varaiants.
Selection pressures - Density dependent factors
Predators
Availability of resources
Nurtient supply
Diease/pathologenic spread
Accumulation of wastes
Selection Pressures: Density Independent Factors
Phenomena
Aboitic Factors
Weather Conditions
Explaining the process of natural selection
-variation
-overproduction of offspring
-Adapations
-Survival Advantage
-Inhertiance
-Progressive change
Lamarckian theory
-finches that arrives on different islands needed to adapt to the available food source in order to survive.
those that adapted passed on these adaptation to the next generation.
-wrong: not based on need, inherited traits that make them better suited to the environment than other individuals of the same species.
Darwinian
-Finches that arrived on different islands encountered different food sources
-Each population had some variation in beak size and shape
-Those finches with the beaks best suited to that environment were better able to survive and reproduce.
Antibotic resistance
- After an antibiotic is developed and used on patients, bacteria showing resitance appear within a few years
- resistance to the antibiotic spreads to more and more species of pathogenic bacteria
- In each species the proportion of infection that are caused by an resistant strand increases
Gradualism
evolution occurs gradually over time
Punctuated Equlibrium
Short period of rapid evolution followed by long periods without change.
Supported by mass extinctions, sudden enviromental change
Reproductive isolation
presents two populations of the same species from interbreeding. it can be temporal, behavioural or geographic. this can lead to specialisation.