Time Machine

Time Machine Context 1

Scientific Evidence of Evolution

• Evolution: observed changes in organisms over successive generations

• Fossil Record: shows progression of species over time showing links between major groups

  • Transitional Forms

    • Intermediate forms between two different groups showing gradual changes over time

    • This form has features of both organisms (eg; A whale with legs - land mammals have legs, fish have whale like qualities)

  • Chronological order

    • Fossils found in chronological order with the oldest layers at the bottom and the youngest at the top (what became before what)

  • Geographic Distribution

    • Certain groups of organisms were widespread but now only found in specific regions

    • Eg; fossils in a certain area can show how long ago they lived, eating patterns, ability to migrate…

  • Anatomical Changes

    • Fossilised bones, teeth etc. show morphology of organisms

      • Comparison to modern organisms - scientists infer evolutionary relationships & track changing in body form and function over time (eg; eating)

  • Vestigial Structures:

    • Fossils preserve structures which aren’t functional in modern organisms but were functional to their ancestors

    • Eg; humans and a tail bone, whales and hip bones

• Comparative Anatomy - Homologous Structures

  • Meaning: comparison of the anatomy of different species

  • Homologous structures: anatomical structures in different species that share a common ancestry

    • could serve different functions in each species but have similar features (evolutionary relatedness)

    • Eg; forelimbs of mammals (eg humans, bats, whales, horse, chicken…) are homologous structures - same bone structure and arrangement, suggesting that species inherited forelimb structures from a common ancestor and adapted to suit specific needs

• Comparative Embryology

  • Meaning: demonstration of similarities in early developmental stages of different species

  • Reveals homologous structures in embryos

    • Eg; embryos of vertebrates (humans, fish, birds, salamanders, reptiles…) have similarities (tails, gills..) suggesting a common ancestor, even though these vertebrates may not have those features in adulthood

Fossil Record & Earth’s Age

• Earliest evidence of life on Earth: 3.5-3.8 billion years ago

  • Simple single-celled organisms (like bacteria or archaea)

  • This was found in Fossil Record

• Over time, fossil record shows increasingly complex life forms

• Life on Earth evolution

1. Single cell organisms

2. Single cell engulf another - eukaryotic

3. Eukaryotic cells make colonies - multicellular life

4. Seae plants, animal life with diversification

5. Plants on land, land mammals

6. Carnivorous forests, winged insects, reptiles

7. Mass extinction event -> mostly dinosaurs left

8. Dinosaurs extinct - the age of mammals

9. Apes split from old world monkeys

10. Humans

Natural Selection

• History

  • Discovered by Charles Darwin

  • Darwin observed many species (animals and plants different from those of the mainland vs islands) that were obviously related but different depending on location

• 4 steps

  • Members of species show variation in their characteristics

  • Some members show favourable characteristics which aid survival and reproduction

  • These members of a species who possess the favourable characteristics survive and reproduce and pass these characteristics on to their offspring. Members of a species without favourable characteristics die out or not reproduce.

  • Over time, organisms with the favourable characteristics will become more common in the population

Population’s Survival

• Genetics:

  • Natural selection needs genetic variations to evolve

    • Mutations (eg; longer teeth, thicker fur, claws…)

      • Changes in the DNA sequence that occur randomly or due to environmental factors (eg; radiation, chemicals)

      • Outcomes: beneficial, neutral, harmful

  • Genetic Diversity allows a population to have a higher chance of survival as they have more individuals with traits to help them cope with a change in the environment

  • Recessive  gene: traits only show up if an individual inherits two copies of the gene (one from each parent)

    • Eg; both parents have brown eyes - therefore the offspring must have brown eyes

  • Dominant gene: the trait which is deemed dominant will be passed down to offspring, and the trait can be from either parent.

    • Eg; one parent has brown eyes and the other has blue eyes. The brown eyed gene is deemed dominant. Therefore the offspring will have brown eyes.

• Environmental Factors

  • Climate & Habitat

    • Temperature or surroundings can endanger or disadvantage the species

    • Eg; a population in a cold environment may have thick fur. Climate change may make the environment warm. Therefore, to survive, the population must adapt.

    • Eg; a population migrates to the mountains (maybe driven out of old habitat by predators). They develop claws and padding on their feet to grip onto the mountain floor.

  • Food & Diet

    • All living things need some sort of food. Populations that depend on a specific food source may not survive if that food source disappears.

    • Eg; a particular soft plant dies due to drought. A population depended on that plant for food. They adapt to having sharp teeth to start eating a tougher plant

  • Predators

    • The presence or absence of predators can create a notable increase or decline in a population.

    • Eg; absence of predators can increase a population, but the population might adapt to a limited way of thinking without a survival instinct. So when predators eventually come, they can easily go extinct. (this is what happened to the dodo)

    • Eg; the presence of predators can endanger a population. Therefore they adapt to avoid being killed. This could be by camouflage, increased speed, moving to a new habitat and more.

  • Disease

  • Pollution

  • Habitat Destruction (deforestation, urbanisation…)

Time Machine Context 2

Structure of the Earth

• Compositional: Materials they consist of

  • Crust: Earth's outermost layer (solid rock). Continental crust (less dense, granite) and oceanic crust (denser, basalt)

  • Mantle: Middle Layer - solid rock, silicates

  • Core: Innermost Layer, Iron & nickel

• Mechanical: Behaviour of the materials they consist of

  • Lithosphere: Outermost, Crust and uppermost part of mantle - Rigid, solid, responsible for tectonic plate movement

  • Asthenosphere: Molten, ductile - where rocks flow slowly, responsible for tectonic plate movement

  • Mesosphere: solid rock, very rigid

  • Outer Core: Molten Liquid iron & nickel - earth’s magnetic field

  • Inner Core: solid, dense, innermost layer - iron and nickel

• Pressure and temp increases the further down you go

Continental Drift

• Continental Drift

  • Discovered by Wegener (Meteorologist)

    • Travelled by balloon to watch these changes in the arctic

    • Universal Rejection of theory (due to being a meteorologist not a geoscientist)

    • Wegener could not understand why the continents were moving

  • The continents used to be one, but they moved apart horizontally

  • Supercontinent: Pangea - formed when the Earth’s landmasses including present day continents were joined together

  • Evidence:

    • Jigsaw fit of the continents

      • Eg; coastlines of South America & Africa fit together. Same story with other coastlines

    • Fossil Correlation

      • Where the fossils remnants of a creature in the past are on coastlines of continents

      • Eg; ancient freshwater reptile fossils found only in two places, southern South America, Southern Africa. Due to being a freshwater animal, it could not swim thru the salty atlantic ocean. They could not have evolved in one location and then travelled to the other without changes.

      • Mostly found where jigsaw continents shown

    • Rock & mountain correlation

      • Eg; mountains of modern day northeastern U.S. same age and type of rock found in U.K. & Northern Scandinavia.

      • Theory: rocks formed at the same time in the same location, but the moving continents teared the rocks apart (later discovered as tectonic plates)

    • Paleoclimate data

      • Theory: By looking at the past climate of the earth, there are glacial striations (makings) which show direction of ice, which is different from the direction where the ice is presently. Therefore, the glacial structures must have moved.

      • Eg; Some glacial striations are going towards the equator (very hot) so Wegener concluded that in the past these locations had been closer to the poles (colder climate)

The Influence of the Theory of Plate Tectonics

• Theory of Plate Tectonics:

  • The Earth’s lithosphere is made up of tectonic plates which are constantly moving slowly but gradually.

  • 20 tectonic plates where continents rest on

  • When plates collide and move suddenly, energy is released as earthquakes

    • Why they occur in specific areas (around tectonic plate boundaries)

    • As molten rock rises from beneath surface, it hardens at spreading tectonic plates, recording orientation of earth’s magnetic field

  • Move a few cm per year

  • Continents will converge again in 250 million years - new supercontinent: PANGEA PROXIMA

• Influence on Continental Drift

  • Advances in tech (warfare) eg; seismometers & magnetometers allowed study of earth.

  • Seismometers

    • Used for nuclear testing ground shaking

    • Monitor ground shaking showed earthquakes in specific regions

  • Magnetometers

    • Used to detect submarines

    • Discovered magnetic variations near undersea ridges (flip flop of earth's magnetic field)

  • Observations support a new theory (PLATE TECTONICS) on wegener's idea

• Structure of the Earth

  • Clarified the layers of the earth

    • Eg; under the crust/lithosphere there is molten rock

      • Mantle

      • Asthenosphere

      • Convection currents in the mantle