recovery programme life sciences gr 10 history of life on...

Recovery Programme Life Sciences Gr 10 History of life on Earth Week 37 Lesson 1 & 2

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Methods of fossil-dating

1. Absolute dating

Matter is made of minute particles called atoms, and atoms are composed of even smaller components.

These components have measurable properties, such as mass and electrical charge. Each atom has a

positively charged nucleus surrounded by negatively charged electrons.

The electric force between the nucleus and electrons holds the atom together.

The atom's nucleus is composed of protons and neutrons, which are much bigger than the electrons.

When an element has atoms that differ in the number of neutrons, these atoms are called different isotopes

of the element.

Radioactive isotopes are unstable and undergo spontaneous nuclear reactions, emitting particles and/or

wavelike radiation. The decay of any one nucleus cannot be predicted, but a large group of identical nuclei

decay at a predictable rate.

This predictability can be used to estimate the age of materials that contain radioactive isotopes.

Geologic time can be estimated by observing rock sequences and using fossils to correlate the sequences

at various locations. Current methods include using the known decay rates of radioactive isotopes present

in rocks to measure the time since the rock was formed.


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Research ‘missing link’ between dinosaurs and birds e.g. Archaeopteryx

This is the size of the Archaeopteryx next to an adult male:

1. Facts about the Archaeopteryx

1.1 The Archaeopteryx may have eaten insects and small animals.

1.2 It lived during the Jurassic Period, about 150 million years ago.

1.3 Its name means “Ancient Wing.” It’s pronounced: ark-ee-OP-ter-iks.

1.4 The Archaeopteryx seemed to be part-bird and part-dinosaur. Unlike modern-day birds, it had

teeth, three claws on each wing, and a long, bony tail.

1.5 Like modern-day birds, it had feathers and a very light body with hollow bones.


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1.6 Length – 30 cm long from beak to tail

1.7 Wingspan – 46 cm long

1.8 Weight – 312 g to 510 g

1.9 Archaeopteryx is one of the oldest-known birds

More of a bird or more of a dinosaur?

• Archaeopteryx lived in the Late Jurassic around 149-151 million years ago.

• Archaeopteryx exhibits both reptilian and bird like characteristics and is therefore known as the

‘missing link’ between birds and dinosaurs.

• Archaeopteryx had wings (although it couldn’t fly), feathers, and a wishbone much like modern birds.

• Archaeopteryx had jaws with sharp teeth, rather than a beak like birds.

• It also had a flat sternum (breastbone). Most modern birds have a keeled breastbone, which allows

them to attach powerful flight muscles.

• Archaeopteryx also had three fingers with little claws on the end of its wings that would allow it to

grasp prey.

• It had extensible second toes known as ‘killing claws’.

• The hallux, or first toe, in Archaeopteryx appears to be flexible, a trait not seen in remains of

dinosaurs.

• It had a long, bony tail.


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Coelacanth as an example of a "living" fossil found off the coast of South Africa

Do you know of any animals that are still alive today that have been living on Earth since the time of the dinosaurs. Some examples are”

• Coelacanths

• Crocodiles

• Horseshoe crabs

• Cockroaches

Evidence suggests that the coelacanth lived 410 million years ago and is still with us today. The same

with…

• Cockroach, 350 mya

• Horseshoe crab, 250 mya

• Crocodile, 200 mya.


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COELACANTHS

First appeared 410 MYA

CROCODILES


HORSESHOE CRABS


COCKROACHES


COELACANTHS

Coelacanths are fish that date from 410 million years ago, but of the original 120 species, only one survived

the event that killed the dinosaurs 65 million years ago.

The surviving species few in number; ate cuttlefish, squids, snipe eels, small sharks, and other fish; and

was dark blue, much like the colour of its ocean habitat.

These animals lived at the same time as the dinosaurs, yet unlike the dinosaurs, they have survived.

Scientists are still debating why these animals have survived.


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The diagram shows an example of a Coelacanth. Some of their fins are lobe-like.

This and many other features have led scientists to believe that they are more closely related to

amphibians than fish.

Coelacanths were thought to have become extinct about 70 million years ago. However in 1938 a living

coelacanth was caught off the coast of East London. A population of about 15 coelacanths have been

found near Sodwana Bay.

Coelacanths are also called the living fossil.

Coelacanths were known only from fossils until a live Latimeria chalumnae was discovered off the coast of

South Africa in 1938.

Coelacanths have a unique form of locomotion. One striking feature of the coelacanth is its four fleshy fins,

which extend away from its body like limbs and move in an alternating pattern. The movement of alternate

paired fins resembles the movement of the forelegs and hind legs of a tetrapod walking on land.

Their jaws are hinged to open wide. Unique to any other living animal, the coelacanth has an intracranial

joint, a hinge in its skull that allows it to open its mouth extremely wide to consume large prey.

Instead of a backbone, they have a notochord. Coelacanths retain an oil-filled notochord, a hollow,

pressurized tube that serves as a backbone. In most other vertebrates, the notochord is replaced by the

vertebral column as the embryo develops.

Coelacanths have an electric sense. Coelacanths have a rostral organ in their snouts that is part of an

electro-sensory system. They likely use electroreception to avoid obstacles and detect prey.

They have tiny brains. A coelacanth's brain occupies only 1.5 percent of its cranial cavity. The rest of the

braincase is filled with fat.


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Coelacanths give birth to live young. After an extremely long gestation period, possibly up to three years,

female coelacanths give birth to live offspring.

They're nocturnal and spend their days resting in caves. During the day, coelacanths rest in caves and

crevices. They leave these daytime resting places the same time late each afternoon to feed, mostly on

fish and cephalopods. Coelacanths are passive drift feeders, moving lethargically near the ocean bottom

and using the current and their flexible lobed fins to move about. They live in the relatively unchanging

environment of deep-sea caves where there are few predators.

CROCODILES

Crocodiles could have survived mass extinction because of their mostly unknown ability to hibernate for

years at a time. They are also smaller than dinosaurs which could also have allowed them to survive.

Crocodiles will also go dormant during long periods of drought.

Theory #1: Crocodiles Were Exceptionally Well-Adapted

Whereas dinosaurs came in all shapes and sizes — huge, elephant-legged sauropods, tiny, feathered dino-

birds, towering, ravenous tyrannosaurs— crocodiles have stuck with pretty much the same body plan for

the last 200 million years. Perhaps the stubby legs and low-slung posture of crocodiles allowed them to

literally "keep their heads down" during the K/T upheaval, thrive in a wide variety of climatic conditions, and

avoid the fate of their dinosaur pals.

\

Theory #2: Crocodiles Lived Near the Water

As stated above, the K/T Extinction wiped out land-dwelling dinosaurs and pterosaurs, as well as sea-

dwelling mosasaurs (the sleek, vicious marine reptiles that populated the world's oceans toward the end of

the Cretaceous period).

Crocodiles, by contrast, pursued a more amphibious lifestyle, perched halfway between dry land and long,

winding freshwater rivers and saltwater estuaries. For whatever reason, the Yucatan meteor impact had

less of an impact on freshwater rivers and lakes than it did on saltwater oceans, thus sparing the crocodile

lineage.

Theory #3: Crocodiles Are Cold-Blooded

Most paleontologists believe that theropod dinosaurs were warm-blooded and thus had to constantly eat to

fuel their metabolisms — while the sheer mass of sauropods and hadrosaurs made them slow to both

absorb and radiate heat, and thus able to maintain a steady temperature. Neither of these adaptations

would have been very effective in the cold, dark conditions immediately following the Yucatan meteor

impact.


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Crocodiles, by contrast, possess classically "reptilian" cold-blooded metabolisms, meaning they don't have

to eat very much and can survive for extended periods in severe darkness and cold.

Theory #4: Crocodiles Grew More Slowly Than Dinosaurs

This is closely related to theory #3, above. There's an increasing amount of evidence that dinosaurs of all

types (including theropods, sauropods, and hadrosaurs) experienced a quick "growth spurt" early in their

life cycles, an adaptation that better enabled them to avoid predation.

Crocodiles, by contrast, grow steadily and slowly throughout their lives and would have better been able to

adapt to the sudden scarcity of food after the K/T impact. (Imagine a teenaged Tyrannosaurus rex

experiencing a growth spurt suddenly needing to eat five times as much meat as before, and not being able

to find it!)

Theory #5: Crocodiles Were Smarter Than Dinosaurs

This is probably the most controversial hypothesis on this list. Some people who work with crocodiles

swears that they're almost as smart as cats or dogs; not only can they recognize their owners and trainers,

but they can also learn a limited array of "tricks". Crocodiles and alligators are also fairly easy to tame,

which may have allowed them to adapt more readily to the harsh conditions after the K/T impact.

The problem with this theory is that some end-Cretaceous dinosaurs (like Velociraptor) were also fairly

smart, and look what happened to them!

HORSESHOE CRABS

Because horseshoe crabs (Limulus polyphemusz) have lived for millions of years in relatively unchanged

form, some biologists refer to them as living fossils. Relatives of the living species have inhabited the

world’s oceans for at least 400 million years. Before their 400-million-year reign began, horseshoe crabs

developed a number of adaptations that allow them to survive, including numerous eyes, hard shells, a

specialized assortment of appendages and a primitive immune-like response to bacteria.

When environmental changes happen, they can move to safety. An ability to live with low levels of oxygen

is also important. The horseshoe crab was able to cope with periods of oceanic deoxygenation that were

fatal to many marine organisms.

Marine biologists identify 10 different eyes and other light-sensing organs on horseshoe crabs. Seven eyes

are on the top of the animal’s carapace; the lateral eyes are the two most obvious, and are compound in

design. Additionally, horseshoe crabs have a pair of rudimentary eyes behind each lateral eye, and a

cluster of three eyes at the front of their carapace. Two very simple eyes are located near the mouth, on

the underside of their carapace, but their function is not clear. The final light sensing organ is located along

the length of their tail; scientists think that they help the arthropods to synchronize their activity pattern with

the lunar cycle.


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One of the most important adaptations of horseshoe crabs is their hard shell, termed a carapace. Though

their carapace does not provide absolute protection from all predators, it discourages the majority of small-

and medium-sized predators.

Many organisms cling to the carapace of horseshoe crabs, including algae, barnacles and mollusks.

Before they develop the hard carapace, young horseshoe crabs avoid the bottom of the ocean, and instead

swim higher in the water column.

Horseshoe crabs have five pairs of walking legs, and one additional pair that has been modified into

chelicerae -- pincers -- that help bring food to their mouth. Horseshoe crabs primarily eat creatures buried

in the sediment. Using their legs, they dig -- primarily at night -- for flatworms, mollusks and other prey.

Horseshoe crabs do not produce antibodies to fight infection. However, they do demonstrate a novel

approach to dealing with pathogens. Presumably, this allows these long-lived creatures to survive in their

bacteria-laden habitats. When a horseshoe crab’s body detects the presence of endotoxin -- a compound

associated with a variety of gram-negative bacteria -- its blood cells begin to exhibit massive clotting. This

effectively seals off the invading pathogens before they can harm the horseshoe crab.

COCKROACHES

Cockroaches are ancient insects that have been around for some 300 million years, and one of the reasons

they've been able to stick around that long is that they're able to change with the times. These insects

survived the mass extinction that wiped out the dinosaurs, and now they're adapting to resist our efforts to

eradicate them.

Cockroaches are not only flexible in the contents of their meals, but also the timing of when they are able to

eat. Some roaches can last more than a month without food and over a week without water.

Perhaps most well-known is that cockroaches can survive a week without its head. If a cockroach loses its

head and later dies as a result, it will typically succumb to dehydration.

No matter how cockroaches produce future generations, one thing they nearly all have in common is that

they're able to produce swarms of new roaches in a short time.

Most cockroaches are night owls. They do their foraging and feeding at night and avoid the light. This

allows them to avoid potential predators and competitors.

Cockroaches have the ability to withstand radiation.

Scientists are still debating why these animals have survived.


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The impact of humans on biodiversity and the natural environment.

Fossil Tourism Fossil tourism is a source of income and employment in some localities.

What impact do we (humans) have on the environment?

Is our contribution positive or negative?

What are the consequences of our impact?

Explain what fossil tourism is and provide a few examples in South Africa,

e.g. Cradle of Humankind – Maropeng (Gauteng)

West Coast Fossil Park – Langebaan (Western Cape)

Kitching Fossil Exploration Centre – Nieu Bethesda (Eastern Cape)

The need for Fossil Tourism and its impact on the economy of the country

List at least five (5) impacts of humans on biodiversity and the natural environment; describe what fossil

tourism is with two (2) examples in South Africa is and how it impacts on the economy.

NB: No answers will be awarded marks in the form of flow charts as diagrams. (20)

Marking guidelines

Rubric table

Relevance (R) Logical (L) Comprehensive (C)

All information given is relevant to the question

Ideas arranged in a logical/ cause effect sequence

Answered all aspects required by the essay in sufficient detail

All information relevant to - Human impact on biodiversity

and environment - Fossil tourism - Advantages of fossil tourism

The information on - Human impact on biodiversity

and environment - Fossil tourism - Advantages of fossil tourism

Is in a logical sequence

The following must be included - Human impact on biodiversity

and environment 3/5) - Fossil tourism (7/9) - Advantages of fossil tourism (

2/3)

1 mark 1 mark 1 mark

Content (17)

Synthesis (3)

(20)

Human impact and Fossil tourism Fossils

Human Impact on Biodiversity and the Natural

Environment.

Some of the treats are listed below:

1. Habitat destruction

2. Natural disasters

3. Over-exploitation

4. Pollution

5. Pesticides and fertilizers

6. Climate change

7. Alien invasive species

8. Disease

Threats to Biodiversity and the Natural Environment

Fossil tourism

Fossil tourism is a type of ecotourism, but in fossil tourism the main attraction is its fossils.

One of the most famous fossils sites is the Cradle of Humankind.

The Cradle of Humankind is found in Gauteng and North West Province.

Fossil tourism

Found in Sterkfontein, Swartkrans, Kromdraai regions.It is a World Heritage Site since 1999.

It is one of the richest source of fossils of early humans.

Nearly half of all human-ancestor fossils have been found here.

Cradle of Humankind

Fossil tourism

The West Coast Fossil Park is found in the Western Cape Province.

It is found along the west coast, a few kilometers inland of the Langebaan Lagoon.

This was once a phosphate mine.

It has the greatest diversity of five million old fossils.

It contained the fossils of the first bear ever found south of the Sahara.

Fossils of the extinct true seal and four extinct species of penguins were found here.

West Coast Fossil Park

Fossil tourism

The many hand on activities at the park that makes it very exciting for the tourist.

Tourists can sift in the sand looking for fossils, with the promise that if you find something new ( no one has found) then it will be named after you.

Plans have been put into place to start a national fossil and rock art route, that joins the Fossil Park to the Cradle.

West Coast Fossil Park

Fossil tourism

Important fossils have been moved to museums once they have been discovered.

The dinosaur fossil found in the Karoo have been moved to the museum in Graaff-Reinet.

The museums become important fossil tourist attractions.

Museums

Fossil tourism

• Situated in the heart of the Karoo, in the town of Nieu-Bethedsa, in the Eastern Cape and it tells the story of life in South Africa 253 million years ago during the Permian Period.

• Life-sized models of prehistoric animals which once lived in the Karoo and paintings by the artist Gerhard Marx illustrate a time when there were no flowers or grasses, no mammals and no birds.

• The Centre also has displays on some of the latest and hottest fossil finds like Homo naledi and Australopihecus sediba.

Kitching Fossil Exploration Centre

https://www.wits.ac.za/homonaledi/

Fossil tourism

Fossil tourism:

1. Creates jobs.

2. Generates income for people living in these areas.

3. Creates business opportunities for travel agents

and tour operators.

Advantages of Fossil Tourism

Terminology:

Fossil tourism is a type of ecotourism, where the main attraction is its fossils.

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