Changes in Species over time

Question 1

Evolution

Answer 1

> Is the change in genetic composition of populations over time
- Can be observed as changes in allele frequencies in a population over time
Genetic change in populations of ancestral species can lead to new species

Question 2

Species

Answer 2

> A species is a group of individuals that are genetically similar enough to produce fertile viable offspring when interbreeding in their natural environment. Can also be thought as a gene pool isolated from another

Question 3

Speciation

Answer 3

> Is the evolution of a new species from an ancestral species
Occurs when genetic differences accumulate through the processes of mutations, natural selection, genetic drift, gene flow, until a new species is formed
2 forms of speciation: allopatric and sympatric

Question 4

What does speciation require?

Answer 4

> A division in the population preventing sub-population from successfully interbreeding
NO gene flow between groups

Question 5

Allopatric Speciation

Answer 5

> A population forms a new species while geographically isolated from its parent population
Occurs when populations are divided by a geographical barrier
The spatial isolation prevents individuals from the sub-populations from interbreeding, leading to genetic differences accumulating, then reproductive isolation and eventually a new species

Question 6

Galapagos Finches

Answer 6

> Are different species of finches living on different islands
Originally there was one ancestral species of finch that colonised the islands from mainland South America: a ground dwelling, seed eating finch.
As the finches on different islands were geographically isolated from each other by the ocean, over millions of years, the ancestral species evolved into many different species.
Each species has a uniquely shaped beak, because individuals with that beak shape have a selective advantage in that particular environment.

Question 7

Adaptive Radiation

Answer 7

> This is were a large number of species rapidly develop from a single ancestral species
Occurs when the ancestral species occupies various niches within an environment, and unique adaptations exist, each favoured by particular selection pressures in their environment

Question 8

Sympatric speciation

Answer 8

> A subset of a population forms a new species without geographic separation

Question 9

Sympatric Speciation

Answer 9

> Occurs without the involvement of a physical barrier, therefore new species are formed from an ancestral species within the same location
Often occurs in plants as a result of polyploidy

Question 10

Isolating Mechanisms

Answer 10

> Different species cannot produce fertile and viable offspring because there are mechanisms that inhibit reproduction from occurring naturally
Although a single barrier may not prevent all gene flow, a combination of several barriers can effectively isolate a species’ gene pool
Typically prevent individuals from different population from interbreeding

Question 11

Reproductive Isolation Before Reproduction?

Answer 11

> Geographical Iso: Populations are separated by physical and geo barriers (oceans)
Ecological Iso: Populations occupy different niches within the same ecosystem
Temporal Iso: The breeding cycles or active time of populations do not overlap
Behavioural Iso: When mating calls an courtship rituals are highly specific. Is only possible in animals
Structural Iso: The reproductive organs of doff species are physically incompatible and individuals are unable to mate
Gamete Mortality: The sperm may not be able to ‘find’ the egg of another species without the appropriate signalling molecules OR the female reproductive tract may no sustain the sperm of another species

Question 12

Reproductive Isolation After Reproduction?

Answer 12

> Prevent a zygote of two different species from developing into a fertile adult
The offspring resulting from interbreeding between individuals from different species are called hybrids

Question 13

Geological Time Scale

Answer 13

> The geological time scale
> The geological time scale allows the history of Earth and evolving life to be chronologically followed.
> Covers events that have occurred from the formation of Earth to the present time.
> Scale is constructed using the order of rocks laid down in a sedimentary rock sequence and the fossilised remains of ancient animals and plants within the rock strata.
>This is a relative time scale in which the oldest rocks are at the bottom.

Question 14

Extinction

Answer 14

> Is a loss of a species or groups of species.
Occurs when:
> Species fail to adapt to environ changes
> Species compete for limited resources.

Question 15

Mass Extinctions

Answer 15

> Occur when the global rate of extinction is much greater than the expected rate of extinction.
May occur due to strong selective pressures, natural disaster, global warming or cooling, asteroid impacts, volcanic eruptions, or disease.
Characterised by a drastic reduction in total biodiversity, leaving previously filled niches empty.

Question 16

Evidence for biological change over time

Answer 16

> Palaeontology
Biogeography
Structural Morphology
Development Biology

Question 17

What is palaeontology

Answer 17

> Involves the study of ancient life represented by fossils.
Fossils are the preserved remains, impressions or traces of organisms found in rocks, amber (fossilised tree sap), coal deposits, ice or soil.
Preserved remains are usually hard structures that are not easily destroyed or are slow to decompose, such as bone, shell, wood, leaves, pollen and spores.

Question 18

The Fossil Record

Answer 18

> The fossil record is the collection of all fossils on Earth, which scientists can use to document patterns of evolution over geographical space and time, within and between species.
Fossils provide information about the kinds of organisms that lived in the past, what they looked like, and where and when they lived.

Question 19

Transitional Fossils

Answer 19

> Is a hybrid fossil that shows traits of both an ancestral group and a descendent group.
Bridge the evolutionary gap between two different species.
Structural similarities between fossils indicate relatedness, which can conclude ancestral origins.

Question 20

Two types of fossils

Answer 20

> Body Fossils: parts of the organism itself
Trace Fossils: Evidence of the organism’s presence

Question 21

How can a body fossil can be formed different ways

Answer 21

Petrification , Mould/cast, Carbon impression, mummification

Question 22

Petrification Fossils

Answer 22

> Formed by the replacement of parts of the organism’s organic material with minerals, converting them into a stone-like fossil.
Harder organic parts such as bone and shell petrify better than softer parts.

Question 23

Mould/Cast Fossils

Answer 23

> Mould Fossils: When the body of a plant or animal decays, leaving an impression in soft sediment.
Cast Fossils: Occurs when the vacant space of the impression mould is later filled with foreign material creating a 3D sculpture of the organism.

Question 24

Carbon Impression Fossils

Answer 24

> Forms when the carbon contained within the organism is deposited onto rock over time, leaving behind a thin, dark film in place of the organism. E.g. leaves

Question 25

Mummification Fossils

Answer 25

> A rare type of fossilisation where the organism is left in its original state.
Organisms have been trapped in a substance under conditions that reduce decay.
> Are not typically found in sedimentary rock.
Unlike other fossilisation processes, the soft parts do not deteriorate away.
Examples include insects trapped in ambers, leaves that still contain carbon, animals frozen in ice or trapped in a peat bog.

Question 26

Trace Fossils

Answer 26

> Do not contain parts of the organism itself.
Are the preserved evidence of an animal’s activity or behaviour.
Examples include footprints, bite marks, burrows, eggs, faeces.

Question 27

Fossilisation

Answer 27

> Is the process that results in the preservation of the hardened remains or traces of organisms.
The process usually occurs in sedimentary rock, due to the layering effect that forms this type of rock, although fossils have occasionally been found in metamorphic rocks.

Question 28

Types of Rock

Answer 28

> Sedimentary Rock: A type of rock that is formed from accumulations of sediment into layers
Metamorphic Rock: A type of rock that arises from the transformation of existing rocks

Question 29

Conditions for Fossilisation

Answer 29

> Rapid Burial: which provides protection and therefore preservation against erosion and other environ damage
Lack of scavengers: Ensures remains are not eaten and specimen is preserved
Lack of decomposers: Ensures organic material of the specimen is not broken down or decomposed
High pressure: Produced as a result of the sediment layers that form on top of the specimen, which promotes mineralisation of the organism’s structures
Lack of oxygen: necessary to protect against decay by decomposers
Presence of hard structures: these structures are replaced by minerals in the fossilisation process

Question 30

Fossil Record Bias

Answer 30

> The chances of an organism becoming fossilised after death are small.
> Soft bodied organisms are unlikely to be preserved because soft-body parts decay readily or are subject to predation and scavenging.
> Fossilised parts of plants are commonly wood and leaves made up of cellulose, which does not decay readily, or spores and pollen which are even more resistant to decay.
Based on the physical and behavioural characteristics of the organism.
> Hard body parts such as bones, teeth and exoskeletons are more likely to be preserved rather than soft body parts such as organs and skin.
> Organisms that live in areas of high sediment accumulation (e.g. near water) are more represented than organisms living on land.
Consequently limits evidence of past life and our understanding of it.

Question 31

Dating Fossils

Answer 31

> The age of a fossil is almost as important as the physical details of the fossil because it gives a time scale of evolution.
The age of a fossil can be determined by:
> RELATIVE DATING
> ABSOLUTE DATING

Question 32

Relative Dating

Answer 32

> Is dating based on stratigraphy.
> The study of the relative positions of the rock strata/layers, some of which contain fossils.
> The lowest stratus is the oldest and the upper strata are progressively younger as sedimentary rock is formed by the accumulation of sedimentary layers on top of each other.
The age of a fossil and/or their surrounding rocks is estimated relative to the known age of a sample.
Can be difficult in areas where rock layers have eroded away, or where rocks have been buckled, moved or reburied, altering the original sequence of strata.

Question 33

Index Fossils

Answer 33

> Are fossils found widespread, existed for only a short time period and have a known (absolute) age.
Used to date and correlate the strata within which it is found.
If the target fossil is found in the same sedimentary layer as an index fossil, then the age of the two fossils will be approximately the same.
If your fossil is found in a higher or lower stratum, then the age can be defined using the principle of fossil succession.

Question 34

Absolute Dating

Answer 34

> Provides a more precise estimate of age. Does not provide an exact date.
Methods of absolute dating include:
> Electro Spin resonance, thermo-luminescence, radiometric dating

Question 35

Radiometric dating

Answer 35

> Is a method of absolute dating that uses the concept of isotope decay to determine the age of a geological sample.
Draws upon naturally occurring radioactive isotopes in the minerals that make up fossils and rock samples.

Question 36

Radioisotope

Answer 36

> Is an unstable form of the element it is named after.
Due to its instability, the radioisotope can spontaneously break down into a more stable product.
> The parent isotope breaks down into the daughter isotope.
> E.g. Carbon-14 (unstable) breaks down into Nitrogen-14 (stable)
Decay at a known rate that is unaffected by pressure or temperature.
This makes them useful as a natural geological clock.
The parent isotope was incorporated into the organism when it was alive and only begins to decay once the organism is dead.

Question 37

Half Life

Answer 37

> All radioactive isotopes consist of an unstable parent isotope that decays into a stable daughter isotope.
The time is takes for half of the parent isotope to decay into the daughter isotope is referred to as a half life.
By measuring the ratio of the amount of parent isotope to the amount of the daughter isotope in the sample, and analysing this against the isotope’s known half life, the absolute age of the specimen can be determined.

Question 38

Carbon-14 / Nitrogen -14

Answer 38

> Carbon-14 allows an estimate of the age of carbon-bearing materials to be calculated up to approximately 50 000 years of age.
Limited to samples not older than 50 000 years because by this age there is very little carbon-14 left.

Question 39

Potassium-40 / Argon-40

Answer 39

> For samples older than 60 000 years, potassium-40, which is found in volcanic rock, can be used.
As volcanic rock cools, its potassium-40 decays into argon-40 with a half-life of 1.3 billion years.

Question 40

Carbon Dating

Answer 40

> All living things absorb carbon from the atmosphere and food sources around them, including radioactive carbon-14 and the stable isotope carbon-12.
> This means, while organisms are alive, they contain the same ratio of carbon-14 and carbon-12 as the atmosphere at the time.
When organisms die they stop taking in carbon. Over time, carbon-12 will remain stable, however carbon-14 decays at a known rate.
By measuring the ratio of carbon-14 to carbon-12 left in an organism, the amount of time passed since the organism died can be determined.
Can date carbon bearing substances up to 50,000 years

Question 41

Radiometric Dating

Answer 41

> Absolute dating can be unreliable if there are very low levels of radioisotope, or if a fossil is too old or too young for the radioisotopes present in the sample.