Evolution

Evolution

the change in heritable characteristics that occurs in biological populations over many years

evolution results in

change in allele frequency over time

what contributes to evolution

natural selection and speciation as well as genetic variation

sources of variation within population

• random mutations

• crossing over

• random assortment

• random fertilisation

evolution occurs to…

a population (NOT AN INDIVIDUAL) over many generations making them better adapted to environment

biodiversity is…

the result of evolution over millions of years

Natural selection process

1. variation in population- due to variation in alleles, differences

2. Selection pressure- certain trait is selected for by environmental factor

3. Survival Advantage- some individual with genetic traits help better adapt to environment

4. Survival of the Fittest- competition for resources mean some individuals are more likely to survive & reproduce passing down the gene

5. Change in Allele Frequency- overtime, more advantageous trait will increase in frequency

Natural Selection examples

• peppered moths in England

• insecticide resistance

• bacterial resistance to antibiotics

Speciation example

• Galapagos tortoises

Artificial Selection

when plants/animals are bred to produce desirable traits

e.g. budgerigars colours

selection pressures

environmental factors acting on a population affecting survival and passing down of a trait

Speciation

1. Variation is present within population

2. isolation- barriers (geographical, reproductive, ecological) prevent allele flow, no interbreeding between

3. Natural selection acts differently as groups face different selection pressures favouring certain alleles changing allele frequency

4. Random mutations occur, further creating differences between the two

5. over Time the two populations become so different can no longer breed to produce fertile offspring

Vestigial structure

Flashcard

body parts that have lost their original function over generations through evolution.

Examples of vestigial organs in humans

• wisdom teeth

• tailbone

• appendix

• piloerector muscles

Example of vestigial structures in other animals

• pelvic bone and femur in whales

• wings in flightless birds

Embryo

An unborn organism that isn’t developed enough to be recognized to a specific species

Common features of verterbrates (chordata) as embryos

• pharangeal slits

• notochord

• tail

• limb buds

Homologous structures

anatomical features in different species that share a common ancestry with same basic structure, may serve different functions

Example of homologous structure

• pentadactyl limbs

• digestive tract in vertebrate

Fossils

preserved remains, impressions, or traces of ancient organisms, found in rock

fossil history of horse

from eohippus 60 mya, 0.4 m height to modern day horse 1 mya, 1.6 m height

main differences:

• bigger body

• longer legs

• decrease in toe number

transitional fossils

the remains of organisms that exhibit traits common to both an ancestral group and its derived descendant group.

• fills in gap in evolution

• shows evolution in process, gradual change

simple life forms from older deeper rock

evolves into more complex forms found in newer upper rock

comparative biochemistry/DNA

Few differences between the DNA of different species, strongly suggests common ancestry/closer relationship

Hominins are…

all humans and bipedal ancestors

hominins have existed for how long on earth?

past 5 million years

features of modern human skull

• centralized foramen magnum for balance

• reduced prognathism from easier diet and balance

• smaller, tightly packed dentition, less chewing needed due to change in diet

• cranial capacity is larger, more rounded, for more brain with more cognitive abilities

nodes represent

common ancestors

species

A group of individuals who are genetically similar enough to produce fertile offspring under natural conditions

natural selection

Process by which an environmental factor act upon population resulting in organisms better adapted with greater chance of survival and reproducing

Fossil Sequence

Shows chronological order of species over time

• from older simple organisms deep to newer complex organisms shallow up

• supports evolution from simple organism to more complex ones

Anatomical Comparisions

• compare anatomy of extinct species to living ones

• reveals homologies suggesting shared ancestry

variation

differences in characteristic due to different genes being present

Survival of the Fittest

The ability to survive and reproduce better than other species in the area