Life Science
NJ ASK Review
8th Grade Science
What is a food chain?
• A food chain is “a sequence of organisms,
each of which uses the next, lower member of
the sequence as a food source1”
Important facts about food chains
• In a food chain each organism obtains energy
from the one at the level below.
• Plants are called producers because they
create their own food through photosynthesis
• Animals are consumers because they cannot
create their own food, they must eat plants or
other animals to get the energy that they
need.
Four types of consumer
• Herbivores: animals that eat only plants
• Carnivores: animals that eat only other
animals.
• Omnivores: animals that eat animals and
plants.
• Detritivores: Animals that eat dead materials
and organic wastes
Other Ways to Classify Consumers
1. Primary Consumers: Herbivores.
2. Secondary Consumers:
Carnivores that eat herbivores.
3. Tertiary Consumers:
Carnivores that eat other carnivores;
an animal that feeds only on secondary consumers.
Identify the producer, one primary consumer, one secondary
consumer and a tertiary consumer.
Tertiary Consumers
Secondary Consumers
Primary Consumers
Producer
Interaction of Organisms
• Predator vs Prey – hunter vs hunted
• Symbiotic Relationships
– Mutualism: both organisms benefit from the
relationship
• Ex: zebra and oxpecker; rhino and birds, shark and cleaner
fish; bee and flower
– Parasitism: one organism benefits, one is harmed ex:
ticks on animals; mistletoe
– Commensalism: one species benefits and the other is
neither harmed nor helped
• Ex: cockleburs; cattle and cattle egrets
Animal vs. Plant Cell
• Determine the similarities and differences.
Animal
• Lysosomes
• Many small vacuoles
• Nucleus is usually in
the center
• Rounded
vs.
Plant
• Chloroplasts
• Mitochondria
• Ribosomes
• Cell Walls
• ER
• Rough
• One Large Central Vacuole
• Smooth
• Vacuoles
• Nucleus usually pushed to
• Nucleus
• Nuclear Membrane the side
• Cell Membrane
• Usually rectangular(ish)
• Cytoplasm
• Golgi Apparatus
Hierarchy of Biological Classification
• Multicellular – living things made up of two or more cells
• Unicellular – living things that are made of only one cell
• Eukaryotic – contains membrane bound organelles such as the
nucleus
• Prokaryotic – no membrane bound nucleus
3 Domains, 6 Kingdoms
Hierarchy of Biological Classification
An easy way to remember…
King
Philip
Came
Over
For
Good
Soup
•
Which taxonomic group includes all the other groups?
Kingdom
•
Human beings are most closely related to other
animals that are in the same ________________.
Species
Domain
The three domains consist of Archaea, Eukaryote and Bacteria
Kingdom
The group that includes all living organisms. There are 5 different
groups which include: Animalia, Plantae, Fungi, Protista and Monera
Phylum
This group splits animals by major characteristics. In example:
Vertebrates are in the Chordata Phylum.
Class
This level of classification divides organisms into more specific groups
such as reptiles and mammals
Order
This level narrows down even further by physical characteristics.
Family
Genus
A family may include animals that live in the same area or have even
more similar characteristics. If turtles were the order, any water turtle
would be in the same family
Further, final breakdown.
Species
Most specific and final step. Pinpoints the exact creature.
Organization of Living Organisms
Cells
-basic unit of an animal’s structure
-become specialized
_______________________________
Tissues
-made of cells that work together to perform a specific function
__________________________________________
Organs
-made of different types of tissues that work together to perform a specific function
____________________________________________________
Organ Systems
-made of organs that work together to perform a specific function
_____________________________________________________________
Organisms
Genetics - What are traits?
• Physical Traits
– Can be seen by others
Eye color, hair color, height, left handed
– Examples:
• Acquired Traits
– Learned skills
– Examples: Playing a sport, riding a bike, playing a musical
instrument
• Behavioral Traits
– Instinctual actions
– Examples: Nest building and migration
• Genotype
Genetics
The genotype is the specific genetic makeup of an individual, usually
in the form of DNA. It codes for the phenotype of the individual.
• Phenotype
An individual’s observable traits. What people can SEE when
they look at you
• Allele
Different forms of a gene, which produce variations of a genetically
inherited trait.
• An individual with non-identical alleles of a gene is heterozygous for
that gene
– Examples: Bb, Tt, Aa
• An individual with identical alleles of a gene is homozygous
gene
– Examples: BB or bb, TT or tt
for that
Terms Used in Modern Genetics
• A genetic factor that blocks another genetic factor is called
dominant
• A genetic factor that is blocked by the presence of a dominant
factor is called recessive
• An allele is dominant if its effect masks the
effect of a recessive allele paired with it
– Capital letters (A) signify dominant alleles;
lowercase letters (a) signify recessive alleles
– Homozygous dominant (AA)
– Homozygous recessive (aa)
– Heterozygous (Aa)
Generation 1
B
B
b
b
In this case we have a dad with black fur and a mother with white fur. Because black is
the dominant gene, we write it with a capital ‘B’. White fur is a recessive trait. It is
written with a lowercase ‘b’. It does not matter what letter we choose to represent a
gene, but capital letter is always dominant and lowercase is always recessive.
Tongue Curling
T=can curl
t=cannot curl
T
t
t
t
Copy into your notebook and complete the Punnett’s Square.
What percentage of offspring will be able to curl their tongue?
When Would a Cell Divide?
Growth
Repair or Replacement
Cancer
Different cells divide at different rates:
Most mammalian cells = 12-24 hours
Some bacterial cells = 20-30 minutes
Mitosis vs. Meiosis
Mitosis – a type
of cell division
that results in
two daughter
cells each
having the same
number and
kind of
chromosomes
as the parent
nucleus, typical
of ordinary
tissue growth.
Meiosis –
a type of cell
division that
results in four
daughter cells
each with half
the number of
chromosomes
of the parent
cell, as in the
production of
gametes and
plant spores.