evolution Flashcards

Question

what did darwin observe

Answer 1

Flora and fauna of the different regions were distinct from those in Europe. Example: rodents in South America were structurally similar to one another, but different from other continents ossils of extinct animals looked very similar to living animals Example: extinct glyptodon and modern armadillo from South America Finches and other animals Darwin saw on the Galapagos Islands closely resembled animals he had observed on the west coast of South America

Answer 2

Organisms produce more offspring than can survive (leads to competition for resources between members of the same species) Individuals of a population vary extensively (comes from inheritable traits) Individuals better suited to local condition survive to reproduce Processes for change are slow and gradual

Answer 3

the study of radioactivity provided geologists with the means to estimate the absolute age of Earth with much greater precision. Every meteorite that has struck Earth has shown to be 4.6 billion years old. Moon rocks were discovered to be 4.53 billion years old. Scientists believe that the Earth has been around for 4.6 billion years.

Answer 4

atoms that undergo radioactive decay, and radioactive decay rates can be measured very accurately. Radioactive decay changes a parent isotope into a daughter isotope of the same element or different element. Each radioisotope decays at its own constant rate, measured in a unit called a half-life This is the time it takes 50% of a sample parent isotope to decay into a daughter isotope.

Answer 5

Favours phenotypes at one extreme over the other. Common in artificial breeding Common during environmental change Example: Peppered moth

Answer 6

Favours intermediate phenotypes and acts against extreme variants of the phenotype Reduces variation Example: Birth weight in humans

Answer 7

Favours the extremes of a range of phenotypes rather than intermediate are favoured Intermediate phenotypes can be eliminated Environmental conditions may favour more than one phenotype. ex: 2 species of plants with different-sized flowers may be available as a hummingbird food source. There may not be any intermediate-length flowers, just small and large.

Answer 8

Favours the selection of any trait that influences the mating success of the individual Combat (caribou) Visual display (Peacocks) Traits favoured in sexual selection include sexual dimorphism (striking differences in the physical appearance of males and females). The most common forms of sexual selection result from female mate choice and male vs male competition

Answer 9

favours extreme phenotypes (i.e. cross-breeding)

Answer 10

favours intermediate phenotypes (“average;” reduces variation)

Answer 11

favours both extreme phenotypes (eliminates intermediate phenotype)

Answer 12

Favours the selection of any trait that influences the mating success of the individual (female mate choice and male vs male competition)

Answer 13

Individuals organisms do not evolve populations do Therefore when we study evolutionary processes we study the changes in population Under a set of specific conditions, a given gene pool (total of all alleles within a population) remains unchanged from generation to generation.

Answer 14

Natural selection: favours the passing on of some alleles over others Small population size: increases the likelihood of genetic drift Mutation: introduces new alleles to a population Immigration or emigration: introduces or removes alleles in a population Nonrandom mating: preferred mates will pass on their alleles more often

Answer 15

A change in the genetic makeup of a population resulting from chance in small populations Smaller populations = GREATER genetic drift and less likely it is that the parent gene pool will be reflected in the next generation Any lost alleles result in a net reduction of diversity of a population

Answer 16

Bottleneck Effect A dramatic, often temporary, reduction in a population size usually resulting in significant genetic drift. Disease, starvation, overhunting, natural catastrophe Only a very small sample of alleles survives to establish a new population Loss of genetic diversity Founder Effect A small number of individuals separate from their original population and find a new population Reduces genetic variation/gene pool Common in islands New “founders” carry some but not all of the alleles from the original population’s gene pool.

Answer 17

The same selective mechanisms found in natural selection are able to account for Speciation - the formation of an entirely new species.

Answer 18

Evolutionary changes that occur at the species level are referred to as

Answer 19

Pre-Zygotic Post-Zygotic

Answer 20

Temporal Isolation Reproductive cycle for flowering or mating occur at different times, even though in the same area. Very common in flower species. Behavioural isolation: Species have a specific signal or behaviour that prevents closely related species from interbreeding. Mechanical isolation Structural differences in reproductive organs can prevent copulation. Ex: The genital in insects operate like a lock & key model Gametic isolation Sperm and eggs of the same species only recognize each other by molecular markers. In other cases, the male gamete cannot survive inside the female.

Answer 21

Zygotic mortality - No fertilized zygotes or embryos develop to maturity E.g. hybrid embryo between sheep and goats die before birth Hybrid mortality - Hybrid offspring are unlikely to live long. Offspring are weak and sterile. Hybrid Sterility - Offspring of genetically dissimilar parents are likely to be strong but sterile. Meiosis fails to produce normal gametes in the hybrid offspring. Example: horse + donkey = mule Mules = sterile

Answer 22

Populations are separated by a geographical barrier and diverge genetically. Gene flow is interrupted Separation can occur due to river, water level change, geological remodelling etc Ex. birds being able to cross large expanses of water versus those that don’t

Answer 23

Populations in same geographical area become reproductively isolated More common in plants than animals New species evolves within a large population For example, a new mutation immediately results in reproductive isolation, but not ecological isolation.

Answer 24

Separation of populations can also threaten the survival of species. Many human activities (agricultural expansion and roads) cause fragmentation of habitats, that effectively isolate populations. → Conservation Efforts to maintain gene flow are now considered. For example, Wildlife corridors connecting strips of forests

Answer 25

Type of allopatric speciation Rapid evolution of a single species evolves into a number of distinct but closely related species, filling a variety of formerly empty ecological niches New resources that were not being used by other species become available Little to no competition

Answer 26

2 or more species with the same ancestors, evolve increasingly different traits, resulting from differing selective pressures or genetic drift.

Answer 27

Similar traits arise b/c different species have independently adapted to similar environmental conditions. Example: sharks and dolphins (streamlined bodies). Example 2: Birds and bats (wings). Both examples don’t have a common ancestor

Answer 28

1 species evolves in response to the evolution of another species 2 species become completely dependent on one another for survival, and their evolutionary pathways become linked. Common among flowering plants and pollinators

Answer 29

As new species evolve, they appear similar to the original species and gradually become more distinctive

Answer 30

Process of evolution is slow, but occasionally there are spurts of rapid change

Answer 31

Three assertions New species evolve rapidly over time Speciation usually occurs in small isolated populations and leaves behind few transitional fossils After the initial burst, additional changes are very slow

evolution Flashcards

(55 cards)