Bio-chapter 10

How are species related

Fossil record

fossil record is the informaiton derived from fossils. The fossil record is arranged in chronological order and helps us map the history of life on earth, placing species in appropriate geological time frame.

• Extinction

• Fossil

• extinction is the dying out of species on a golbal or regional level.

• Fossil is the preserved body impression or traces of a dead organism.

• Fossillisation

• Sediment

• sedimentary rock

  → types of fossils (PMCT)

• permineralised fossil

• Mould fossil

• Cast fossil

• Trace fossil

• fossillisation is the process by which an organism becomes a fossil.

• Sediment is a naturally occruing solid material such as earth and rock, that is broken down into very fine pieces and typically settles at the bottom of liquid

• Sedimentary rock is a rock that has formed though the accumulation of sediment that hardens under pressure

• permineralised fossil is a fossil that is formed when a mineral-rich groundwater deposits mineras like silica and calcite into organic material, creating a mineral relic

• Mould fossil is a fossil formed when a living organisms decomposed underneath a sediment creating a cavity in the shape of the dead organisms.

• Cast fossil is a fossil formed when a mould fossil is filled with sediments.

• Trace fossil is a fossil or a structure indicating the presence of an organisms, rather than the organisms themselves (nests, footprint).

The process of fossilisation (ROW)

1. Remnants of organims are rapidly covered by sediments, meaning that the dead organims is not exposed to oxygen, microorganisms and other disturbance that would increase rate of decomposition.

2. Over time sediments layers build upon each other and compact, layer by layer, until pressure cements them together to form sedimentary rock.

3. Within this rock, the fossilised remains can take many from including permineralised, mould, cast and trace fossil.

Conditions Favouring Fossilisation:

Certain conditions increase the likelihood of fossilisation, including: (BARCA)

-Buried quickly: Rapid sediment accumulation to cover the organism.

-Away from scavengers: Protection from scavengers and decomposers (e.g., fungi, bacteria) is crucial for preservation.

-Reduced oxygen: Reduces the activity of decomposers that require oxygen.

-Cool Temperature: Cooler environments slow down decomposition processes.

-Absence of light: low light levels helps prevent decomposition.

using fossil record

Relative dating (3 types)

• relative dating is a way to estimate the age of a fossil by comparing it to to other fossils or sediment layer (strata) it’s found in. 3 types of relative dating are succession fossil, index fossil and transitional fossil.

• absolute dating is using a radioactive decay to find a fossil’s actual age in years. Also known as radiometric dating. type of absolute dating is radiometric dating

• Absolute age is an estimate of the age in years of a fossil or rock.

Strata- single layer of the sedimentary rock

Stratum- multiple layer of the sedimentary rock

mummification- organisms is left in its original state which has been trapped in a substance under conditions that reduce decay and experience little change.

Geological timescales

Fossil succession the principle that fossils of the same age will be in the same layer of the sedimentary rock, with the oldest being at the bottom and the youngest at the top.

Scientists use the law of fossil succession to build a timeline of Earth’s history.

Each rock layer (stratum) gets matched to a time period.

if you know the age of a layer, you can estimate the age of any fossil found in it.

2. Index Fossil

Index fossil is a group of widespread fossils that existed for a short period of time and have a known age. it can be used as a reference to determine the age of the unknown fossils.

-for the best index fossils species must be: WIDE

• Widespread (found in many places)

• Indetifiable (physically distinctive)

• Dated(from a known short time period)

• Everywhere (large populations)

Transitional fossils

Transitional fossils is a fossil that shows trait that are common to both ancestral group and the descendent groups. they are particularly important when the descendent species is very distinct to the ancestral species, such that the transitional fossil helps demonstrate evolutionary changes between the two.

• imagine species X is a defender and species Z is a striker. a transitional player (species Y) is a midfielder- sharing traits of both.

Absolute dating

-Radiometric→ specifically radiocarbon dating

Radiometric Dating is a technique that uses radioisotopes to find the absolute age of a fossil.

Radiocarbon is a type of Radiometric dating.

• used for organic material (bones, wood, plant)

• works best for things that died within the last 50000 years.

How it works (basic principles)

1. Radioisotopes are unstable atoms that are broken down (decaying) into stable ones over time. e.g Carbon-14 breaks down into Nitrogen-14.

2. This Breakdown happens at a constant rate, measured as half-life.

   -Half-life is the time it takes for half of the radioactive atoms to decay. e.g 14’C half-life=5730 years.

3. Scientists compare:

   -How much radioisotopes (like 14’C) is left in the fossil

   -To how much is found in the atmosphere or stable product.

   -This ratio tells us how many half-lives have passed and therefore the age.

10B- Evidence of relatedness

a single species can evolve and eventually become two separate species. This means that there’s some level of relatedness between different species. one method to assess this relatedness is through Structural morphology, which is the study of physical features to establish relatedness.

Homologous structures

Homologous structures are features present in two or more species that may look and function very differently in each species but are derived from a common ancestor.

SAME STRUCTURE, DIFFERENT FUNCTION → COMMON ANCESTOR as ‘HOMO’ means same

e.g human arm, cat leg, whale flipper, bat wing.

used for different things: carrying, walking, swimming, flying, but the bone structure is the same.

Analogous structure

Analogous structure are features present in two or more species that fulfil same function but do not originate from same ancestor.

DIFFERENT STRUCTURE, SAME FUNCTION → NO common ancestor

e.g Bird Wings VS Insect Wings

both are used to fly

but Birds and insects are not closely related.

Vestigial structure

Vestigial structure are features that have lost some or all of their usefulness as a result of natural selection.

e.g: HUMAN- Appendix is for digesting cellulose in a plant-heavy diet.

SNAKES- pelvic bones ancestors had legs for walking.

Molecular homology

Molecular homology is the comparison of DNA and amino acid sequence between species to determine evolutionary relationships.

• Amino acid similarity

Amino acid sequence similarity focuses on proteins made for amino acid that are

• found in many species (conserved)

• used to compare how closely related species are

• The fewer the differences in amino acid sequence between species, the more closely related they are. like the protein that carries oxygen in red blood cells.

DNA sequence similarity

DNA sequence similarity involve comparing the order of nitrogenous bases in the DNA of two or more species.

• The more similar the DNA the more closely related the species are.

• Fewer nucleotides differences= more recent common ancestor

• this is more precise compared to amino acid similarity which is easier to interpret.

10c

phylogenetic trees

Phylogenetics is the study of the relatedness between organisms.

-Phylogenetic tree is a diagram used to show relatedness between organisms.

-Evolutionary relationship is the relatedness of organisms based on shared ancestory.

-lineage is a direct sequence of organisms that evolved from a common ancestor.

Taxa is a unit of biological classification into which related organisms are classified. Taxa arranged in a hierarchical rank from kingdom to species, where members of a specific taxon typically share certain morphological characteristics.