BIOL1101 - evolution and biological diversity

What is the definition of extinction?

Loss of all living members of a species.

List the periods of the 5 big mass extinctions and the dates.

Ordovician 450-452 million years ago, Devonian 359-385 million years ago, Permian 250 million years ago, Triassic 205 million years ago, Cretaceous 65 million years ago.

What was the aftermath of the late Ordovician mass extinction?

Sharks, bony fish and ammonites radiate. Land is colonised by plants and arthropods

what is the meaning of trophic status in regards to deterministic causes of extinction?

animals with a higher level of extinction have a greater chance of extinction. This is because they have fewer offspring in a lifetime and have a ling onset to sexual maturity.

stochastic factors that might cause a species to go extinct include: a. Over specialisation b. Poisoning of the atmosphere from volcanic eruptions c. Slow rate of reproduction d. Inability to effectively avoid predation

b (Note - a, b, and d are deterministic factors)

which of the following statements is true: a. Deterministic traits are the major driver of mass extinctions b. Genetic variability within populations is essential for avoiding the extinction vortex c. Stochastic processes have only subsidiary influence over the structure and diversity of life d. None of the above

b (note: c has a major effect)

What is the definition of deterministic traits?

deterministic traits are characteristics of the organism that make them more or less susceptible to extinction (intrinsic factors).

What caused the late Ordovician mass extinction?

drop in sea levels due to Gondwana glaciation (glaciers/ice sheets forming) which cooled and reduced eco-space.

What was the aftermath of the late Devonian mass extinction?

extensive forests, radiation of insects, first reptiles (life cycle wholly on land).

List the deterministic causes of extinction (6)

geographic range, rarity, specialisation, popular variability, trophic status, and intrinsic rate of population

what is the definition of evolution?

it is a progressive trait change across generations.

what in general causes mass extinction?

it is a result from extraordinary/sudden changes in the environment.

How are mass extinctions observed now-a-day?

it is observed through major biostratigraphic changes within sediment sequences. Specifically the disappearance of old species and the appearance of new species.

what is the meaning of popular variability in regards to deterministic causes of extinction?

it means low genetic variability, therefore more likely species will succumb to disease, introduced predators, competition, etc. because the species isn't likely to adapt.

what is the meaning of intrinsic rate of population increase in regards to deterministic causes of extinction?

it means the inability for a species to recover/reproduce quickly and efficiently after major disruptions, therefore meaning they have a greater chance of extinction.

Describe the extinction vortex.

it starts off with a small population, and since it's small there is large amounts of inbreeding. As a result there's a loss of genetic variation which impedes evolutionary responses to environmental change. This vortex will lead to extinction.

describe Earth's second atmosphere.

it was created by volcanoes releasing gas, predicted to be water, carbon dioxide, sulfur dioxide, carbon monoxide, nitrogen and hydrogen. There is no free oxygen. Ocean formation occurred as the earth cooled, water produced by out gassing could exists as a liquid in the early Archean, allowing oceans to form. an environment amendable to life.

what is the meaning of rarity in regards to deterministic causes of extinction?

lower population size equals greater chance of extinction.

what is the meaning of geographic range in regards to deterministic causes of extinction?

smaller distribution equals greater chance of extinction.

What organisms was made extinct from the mixture of deterministic and stochastic processes? How?

the heath hen. They started out fairly abundant on a large geographic range but were hunted and as a result decreased the population and range rapidly. Major wildfire followed by a harsh winter, predatory goshawk, and disease caused the hens to become extinct.

What forces a global state shift? (8 factors)

- Habitat fragmentation - Landscape alteration - 40% of land covered to agriculture - Global pollutants and dead zones (not a lot of dead zones in Australia, dead zones have very low oxygen levels in water) - Green-house gases - Increased pestilence - Species loss - they often maintain their own environment - Water loss

Question: Which of the following is not an observation or inference on which Darwin's theory of natural selection is based? 1. Poorly adapted individuals never produce offspring. 2. There is heritable variation amongst individuals. 3. Because of overproduction of offspring, there is competition for limited resources. 4. Individuals whose inherited characteristics best fit them to their environment will generally produce more offspring. 5. A population can become adapted to its environment.

1

what are 2 key points of natural selection?

1. NS does not create new adaptions - it selects for existing variation. In HIV drug resistance the presence of the drug destroys all but the rare individuals with resistance. 2. NS depends on time and place, what is adaptive in one time and place may be useless or even harmful in another. This is referred to as "modes of selection"

What are Darwin's observations in regards to the theory of evolution? (5)

1. all species produce so many offspring that if all survived their population would increase exponentially (this wouldn't happen) 2. yet populations tend to remain stable in size apart from seasonal fluctuations 3. environmental resources are limited 4. individuals of a population vary extensively (No two individuals are exactly alike (apart from identical twins)) 5. much of the variation is heritable

What are Darwin's inferences in regards to the theory of evolution? (3)

1. the production of more offspring than the environment can support leads to a struggle for existence with only a fraction of the offspring surviving each generation 2. the struggle for existence is not random - those individuals whose inherited traits best suited to the environment are more likely to have more offspring than other (less fit) individuals. 3.the unequal ability of individuals to survive and reproduce will lead to a gradual change in population with favourable characteristics accumulating over generations.

what did the end-Cretaceous mass extinction effect?

16% marine families, 17% of land vertebrates, all dinosaurs (except birds), pterosaurs, marine reptiles and ammonities.

What did the late Ordovician mass extinction effect?

25% of animal families, including most trilobites, brachiopods, bryozoans, and corals. Topical marine groups worst hit

How old is the earth's aged predicted to be based on scientific estimate?

4.54 billion years old

What did the late Devonian mass extinction effect?

85% of plankton, 20% of animal families, all armored fishes, most jaw-less fishes, and almost all reed-building groups (reef area shrank by order of 5000)

What did the end Permian mass extinction effect?

90-95% of all species. 70% of terrestrial plants, insects, vertebrates and many marine groups. Almost all groups affected, many (e.g. trilobrites) completely disappear. (note - this was the most severe extinction of all time).

why did the end-Cretaceous mass extinction occur?

A large asteroid impacted on Mexico resulting in Volcanic eruptions in India. Also, climate change was making the earth cooler and drier which also effected the organisms on earth before the asteroid.

what caused the late Devonian mass extinction?

Drastic global cooling (therefore mostly warm-water species lost), changes in ocean chemistry (reduced oxygen), and Extra-terrestrial impacts

What is the definition of ecologically extinct?

Species still persists, but so rare it doesn't have a role in the ecosystem any more.

What is the definition of extant?

The species is still living/not extinct.

Is extinction a natural process?

Yes, extinction has been happening since life first originated and it is a key evolutionary process which creates opportunities for other species.

mass extinctions: a. Typical mark the boundaries between major divisions of the geological time scale b. Are mostly an artefact of an incomplete fossil record c. Are invariably caused by instantaneous events like comet impacts caused by factors such as extreme climate change d. Have no biostratigraphic utility

a (note, b = minor extinctions episodes probably yes, but not mass extinctions, c = no, they can occur over several million years and be, d = untrue, they are very useful in this regard)

why did the end-Permian mass extinction occur?

a massive comet/asteroid hit earth, setting off massive volcanism in Siberia. This resulted in huge amounts of carbon dioxide and sulfuric acid being released.

describe the first atmosphere.

made of hydrogen and helium which was quite rare on earth compared to the universe because earth's gravity wasn't strong enough to hold lighter gases. Earth didn't have a differentiated (solid inner/liquid outer core) core which creates earth's magnetic field which defects solar winds. Once the core differentiated the heavier gases could be retained.

what was the aftermath of the end-Cretaceous mass extinction?

mammals radiated into niches vacated by dinosaurs and marine reptiles. Birds, gastropod molluscs, pollinating insects and flowering plants diversify.

What was the aftermath of the end-Permian mass extinction?

only 5-10% of species survived. They founded diverse biota, including dinosaurs, mammals, invertebrates, fishes and plants.

what is the meaning of specialisation in regards to deterministic causes of extinction?

organisms that only eat certain food and/or lives in a certain habitat have a greater chance of extinction.

what is the definition of stochastic processes?

these process are extrinsic factors or unexpected events that make species vulnerable to extinction due to chance alone.

what are mass extinctions?

they are geologically rapid loss of a large and diverse array of organisms.