Critical thinking

1
Critical thinking
2
Scholarship criteria The student will use
biological knowledge and skills to analyse
biological situations and integrate ideas into a
coherent response. For outstanding performance,
the student will demonstrate perception and
insight in the analysis and integration. (Biology
Scholarship standard, Ministry of Education)
3
Scholarship students are expected to demonstrate
high level critical thinking, abstraction and
generalisation, and to integrate, synthesise and
apply knowledge, skills, understanding and ideas
to complex situations. (Scholarship Performance
Reference Group)
4
Question 3, 2004 Scholarship Biology
5
The three examples shown represent just some of
the diversity found in bony fish. Use the
diversity of the fish and/or any other named
group(s) to discuss the following
statement Diversity is the end product of
evolution.
6
Candidates who did not achieve the standard
tended to describe rather than discuss in
Question 3, and while there were a lot of
descriptions of the diversity in fish, there was
little or no attempt made to discuss the
evolutionary processes that resulted in this
diversity. Candidates gave their own opinion as
an evaluation.
7
Overall Successful candidates addressed the
question asked, with minimal irrelevant material
presented. Answers were coherent with ideas
integrated, and it was clear these candidates
spent time planning their answers and organising
their ideas. Unsuccessful candidates wrote in
generalisations rather than specifics e.g. it
evolved by natural selection. They tended to use
inappropriate descriptors e.g. catastrophic,
terrible, rather than biological terms.
8
Critical thinking means seeking reliable
knowledge. Many students fail to assess the
reliability of information to which they are
exposed in everyday life, let alone pursue the
dissection of scientific literature. And many
people are deceived and defrauded by
pseudoscience. Practice in critical thinking
prompts thoughtful examination of the role of
science in society.
9
Wind farms bird kills
10
Wind farms bird kills In the United States
(where some of the earliest wind farms were
poorly sited in areas where there were lots of
bird movements), a study shows that between
10,000 and 40,000 birds are killed by turbines
each year. This seems like a lot and a good
reason to reconsider the use of wind farms
11

• However, you need to consider the other causes of
  bird deaths. In the US
• cars trucks kill 60 80 million birds per
  year
• buildings/windows kill 98 980 million per
  year
• communication towers kill 4 50 million per
  year
• the biggest killers of birds are domestic wild
  cats, which are estimated to kill up to a billion
  birds every year.
• Environmental scientists in NZ say that as long
  as care is taken about where we site wind farms,
  they present only a very small danger to birds
  bats.

12
Food allergies, vitamins, overgeneralisations
13
Many people cant drink milk, due to an allergy
or intolerance. However, milk contains a lot of
nutrients - so the r.d.a. is 2 servings/day for
an adult. Still, for some people its quite
harmful if they cant tolerate milk (or any
food) they shouldnt eat it just because its in
the healthy foods pyramid! In other words,
evaluate by the principle of individuality by
your own uniqueness.
14
However, someone may become quite sick after a
glass of milk. Instead of properly evaluating the
situation and saying "I should not drink milk,"
they instead overgeneralise and say "Milk is bad
... no one should drink milk." This is
overgeneralising from personal preferences. The
principle of individuality will help to
counteract this tendency to evaluate a person, or
group of persons, or a food, as being all bad or
all good and then projecting our expectations
onto all our encounters with this person or food.
15

• Or look at Vitamin A its a "vitamin" so it
  must be good for us! This is a common perception.
  
• However, Vitamin A can be lethal. The recommended
  daily dose of Vitamin A is around 1,000 Retinol
  Equivalents each day
• Ingesting 5 REs a day will eventually lead to
  death from Vitamin A deficiency.
• Taking in 100,000 REs a day will lead to
  hypervitaminosis A eventual death.

16
Many people have made themselves sick and even
killed themselves by disregarding the
individuality of dose. A little may be good for
you, but a lot may kill you. Even plain water can
kill you if you drink too much.
17
Saccharin cancer
18
Saccharin is a non-calorie sweetener widely used
in foods since World War I. Up until the 1970s
many diabetics weight watchers used saccharin
as a sugar substitute. A 1977 study of rats
found that saccharin could cause cancer. The FDA
banned saccharin from the food supply, though
this has since been reversed many people remain
fearful of saccharin.
19

• BUT
• Saccharin has been found to cause cancer only in
  one species rats. It does not affect many other
  species, such as monkeys, mice and guinea pigs.
• Among rats, saccharin caused an increased
  incidence of bladder cancer in male rats, but not
  in female rats.
• Yet the media focussed on labelling saccharin a
  "carcinogen" without reference to species, as if
  a carcinogen in rats will automatically be a
  carcinogen in humans.

20

• By 1990, 392 chemicals had been tested for
  carcinogenicity in both mice and rats.
• 226 were found to cause cancer in at least one
  species however 42 of these carcinogens caused
  cancer in ONLY one of these species!
• There is clearly significant variability between
  species in cancer risks. If nearly half the known
  rodent carcinogens can't be generalized from one
  rodent species to another, how can we confidently
  generalize from male rats to humans?

21
The media also tend to overgeneralise between
reporting of "carcinogens" and the way we test
chemicals for carcinogenicity. The rats in the
saccharin experiment received the equivalent of
someone drinking 800 cans of diet coke every day!
This high dose was selected so that relatively
few animals could be used. BUT a substance may
have different effects at different doses. No
human would drink anywhere near that amount of
saccharin in one day, let alone each day for
their entire life!
22
However, the media reported the study as if the
dose were irrelevant. In fact, several essential
nutrients in humans, including selenium and
retinol (a form of Vitamin A), cause cancer when
fed in high doses to some animal species. If we
applied saccharin standards to these essential
nutrients they would have to be banned from the
human food supply.
23
In 1989 came the announcement that dioxin had
been found in milk served from paper cartons. The
dioxin had leached from the paper cartons into
the milk. Newspaper stories of the
dioxin-tainted milk invariably referred to dioxin
as a carcinogen, implying that increased
incidence of cancer would await the children
exposed to the tainted milk.

• However
• Dioxin had been found to be a carcinogen in some
  animal species, but not in others.
• And it had been found to decrease the risk of
  some types of cancers in some species. Dioxin, in
  other words, could just as truthfully be called
  an anticarcinogen.

24

• A second media over-generalisation involved the
  amount of dioxin in milk
• Most milk samples tested revealed no detectable
  dioxin, but the highest amount of dioxin in a
  tainted sample was measured at 0.07 parts per
  trillion (ppt).
• 0.07 ppt is equal to 70 nanograms of dioxin in
  1200 litres of milk.

25
Rats the safety of GM diets
26
In a 1998 experiment, rats were fed GM potatoes
the potatoes contained a gene from snowdrops that
expressed the protein lectin. Lectin can act as a
natural pesticide.

• The researchers fed groups of rats one of these
  menus
• lectin-boosted modified potatoes,
• unmodified potatoes,
• or unmodified potatoes plus lectin from a
  bottle.

27

• What the study found
• Eating potatoes with lectin (in any form) was
  associated with a thickening of the mucus
  membrane lining the stomach.

• In rats that ate only raw genetically modified
  potato, the mucus-producing pits of the small
  intestine were longer, compared to other rats in
  the study.
• Rats eating transgenic potatoes had fewer
  lymphocytes compared to those eating normal
  potatoes.

28

• The scientists conclusions
• Eating potatoes modified to produce lectin
  caused some cells to grow, and others to fail to
  grow, in the stomach and intestine.
• At least some of these effects were due to the
  foreign gene. Other effects could be due to the
  process of genetic engineering itself.
• The genetic modification process could cause
  similar outcomes when used to move other genes.

29

• Rats GE diets what was wrong with this study?
• Too few rats only six per food type were
  used.
• Poor diets all the rats ate pure potatoes,
  which contain only 6 protein (normal lab rats
  get 15). "There is convincing evidence that
  short-term protein stress and starvation impair
  the growth rate, development, hepatic liver
  metabolism and immune function of rats."
• There was no control group no group of rats
  ate a good rat diet for comparison.
• Critics maintain that no consistent patterns of
  changes were observed during the study.

30
Food irradiation
31

1. Discuss techniques that scientists could use to
   detect DNA damage in microbes. What key factors
   would have to be considered? Use diagrams if
   necessary.This question is testing the
   application of certain genetic and other
   techniques and the ability to consider key
   factors in designing experiments. This tests some
   of the skills of practical investigation.

32

• The safety of food irradiation is a controversial
  issue in New Zealand at the moment. There is not
  enough information given above to fully evaluate
  this issue. What questions would you ask of
  scientific experts and what information would
  gather before you could make an informed choice
  as to whether food should be irradiated?
• This is testing the skills of evaluating issues.
  The first thing to work out here is the key
  issues highlighted earlier. Notice that you are
  asking questions, not necessarily answering them.
  The ability to know the questions to ask is a
  really important skill. Also, this is a science
  paper, so you will be wanting hard data!

33

• Consider these questions under the following
  headings
• The effectiveness and safety of gamma rays.This
  question is about gamma rays. So immediately
  recall your knowledge about the penetration of
  gamma rays. Think about how the radiation source
  is used and how it is stored.

34
(ii) Consideration of the relative risks
involved in irradiating food.This is testing
the skills of writing a case study. Go through
the passage carefully and consider the arguments
for either side of this debate. Also consider
relative risks, e.g. methyl bromide can be used
for destroying exotic pests but it harms the
ozone layer. So is radiation a better option
here?Consider things like the incidence of food
borne diseases one question you may want to ask
experts or find out more information about is how
serious a problem this is. What else may you
want to find out about?
35
Osteichthyes http//ipimar-iniap.ipimar.pt/DITVP
P/site/introducao/fish.htm Seahorse http//www.af
cd.gov.hk/conservation/images/cop12/Seahorse203.j
pg Anglerfish http//earthguide.ucsd.edu/hughes20
01/acct/bmounmanivong/lifethatglows/anglerfish.htm
Tararua wind farm http//www.ourregion.co.nz/gI
mage.php?gImageID571gallery4regionID Irradiati
on cartoon http//www.msu.edu/user/sawyerc/outlin
e-1-wilson.htm