Life Sciences Paper 1 Notes
Reproduction in Vertebrates - 5%
● Diversity of reproductive strategies
Human Reproduction - 27%
● Introduction
● Structure of the male reproductive system
● Structure of the female reproductive system
● Puberty
● Gametogenesis
● Menstrual cycle
● Fertilisation and development of zygote to blastocyst
● Implantation, gestation and the role of the placenta
Responding to the environment (humans) - 36%
● Introduction
● Human nervous system
● Central nervous system
● Peripheral nervous system
● Autonomic nervous system
● Structure and functioning of a nerve
● The simple reflex arc
● Disorders of the CNS
● Receptors
● Human eye
● Human ear
Responding to the Environment (plants) - 9%
● Plant Hormones
● Plant defence mechanisms
Endocrine and Homeostasis (humans) - 23%
● Endocrine system
● Introduction - homeostasis
● Homeostasis: Negative feedback mechanisms
1
,Reproduction in Vertebrates
Key Terminology:
Reproductive strategy Structural, functional and behavioural adaptations that improve
the chances of fertilisation and the survival of offspring
External fertilisation Fertilisation that takes place outside the female’s body, usually in water
Internal fertilisation Fertilisation that occurs inside the female’s body where the male has
deposited its sperm
Ovipary Eggs are laid; the embryo develops outside the mother’s body
Ovovivipary Young develop from eggs fertilised internally and retained within the
mother's body after fertilisation until they hatch
Vivipary The young develop inside the uterus of mother after eggs are fertilised
internally; young are nourished through the placenta
Amniotic egg The embryo inside the egg is protected by a hard shell; the egg consists
of many extra-embryonic membranes that serve different functions
Extra-embryonic membranes Membranes that surround the developing embryo inside the amniotic egg
or uterus.
Amnion Produces amniotic fluid which cushions embryo and protects it from
mechanical injury, temperature changes, dehydration
Allantois Collects the embryo’s nitrogenous waste and assists in the exchange of
gases
Chorion Allows for gaseous exchange in the amniotic egg and forms the placenta
in mammals
Yolk sac Contains the food reserves for the developing embryo
Precocial development When hatchlings are well developed as they hatch, able to move and feed
themselves, with eyes open – limited parental care
Altricial development When hatchlings are underdeveloped as they hatch, unable to move or
feed or fend for themselves – young require more parental care
Parental care Includes the building of nests, protection, teaching of young and feeding
– the care, or lack thereof, directly influences the survival of the young
,External fertilisation and internal fertilisation
● Fertilisation occurs when a haploid sperm cell and egg cell fuse to form a diploid zygote.
External fertilisation Internal fertilisation
Takes place outside female’s body - Requires water Takes place inside female’s body - No water required
Gametes released into water - Spawning - prevents Sperm cells are released into the female’s body
drying out. Egg attracts sperm Not limited to aquatic environment
Little cooperative behaviour A lot of cooperative behaviour
Low chance of fertilization High chance of fertilization
Many gametes released - increases chance of fusion Fewer gametes released - better chance of survival
Many offspring produced Fewer offspring produced
High mortality rates among young due to lack of Lower mortality rates among young as protection is
protection. Eggs can easily desiccate/be predated on. provided by the mother’s body or a hardened
Offspring is independent calcareous / leathery shell. Offspring is dependent
Fish and amphibia Terrestrial vertebrates - reptiles; birds and mammals
Ovipary, ovovivipary and vivipary
Ovipary Ovovivipary Vivipary
Fertilisation external or internal internal internal
Development External to the body of the Inside the body of the female inside the uterus of the
of embryo female - in egg The egg is laid as soon as the female
embryo is fully developed
Nutrition Yolk is form of nutrition Yolk present in the egg. Young receive nutrition from
Aquatic eggs - Less yolk (less the mother’s body through
energy to produce) Young are independent of the placenta
Terrestrial eggs - More yolk the mother’s body
(More energy to produce)
Type of egg Jelly-like or calcareous Calcareous or leathery None
Examples fish, amphibians, reptiles, birds Sharks, lizards and snakes Humans
Amniotic egg
● Water protects aquatic vertebrates eggs from drying out and assists with fertilisation
● Some terrestrial animals need specialised structures to protect the developing embryo from drying out
● Functions of the amniotic egg:
○ Prevents dehydration of the embryo, Provides nutrients (water & oxygen), Remove Waste products
Structure: Function:
Amnion Surrounds the embryo and protects it against shocks,
injuries, temp changes and dehydration
,Allantois Sac that extends from the embryo’s intestines and
collects waste products and exchanges gases
Chorion Outermost membrane.
Bird/reptiles have porous shells for gaseous exchange.
Mammals forms part of the placenta - supplies foetus
with nutrients and helps with gaseous exchange and
excretion
Yolk sac Energy rich yolk provides food for embryo
Albumen Serves as reserve food
Shell Hard, calcareous, leathery and porous for gaseous
exchange - protects embryo
Precocial and altricial development:
Precocial Altricial
Offspring are fully developed and can move around directly Offspring are not fully developed and cannot
after birth move around immediately after birth
Few offspring are produced as lots of energy is used in More offspring are produced
getting to the advanced stage of development before birth
Offspring is faces challenges of environment Parental care afforded to protect from predators.
Less energy used in care of offspring after birth More energy spent on care of offspring are birth
Large amount of yolk for extended incubation period Eggs are smaller and contain less yolk
Mammals: Long gestation period Mammals: Young born ASAP as mothers are
vulnerable to predation
Covered in hair or feathers No hair or feather covering body
Offspring can protect and feed themselves Offspring cannot protect and feed themselves
Parental Care:
● Behaviour of parents in caring for their offspring = Increases chances of survival of the young.
● Eg: Guarding and incubation of eggs, Keeping the young warm, feeding them and protecting them from
predators
● High parental care = low prenatal energy/few offspring produced
● Low parental care = high prenatal energy/many offspring produced
Fish amphibians Reptiles Birds Mammals
No PC Little/no PC Little/no PC A lot of PC Highest PC
Eggs are abandoned Protect eggs Sun incubate eggs Builds nests/ feed Protect young
,Human Reproduction
Key Terminology:
Gamete An egg or sperm cell with half the number of chromosomes
Gametogenesis The process in which gametes are produced in the testes and ovaries through
meiosis oogenesis the process that occurs when egg cells are made in the
ovary through meiosis
Spermatogenesis The process that takes place when sperm cells are made in the testes through
meiosis
Germinal epithelium Cuboidal epithelium found on the surface of the testes and ovaries which gives
rise to the cells which mature to form sperm cells and egg cells respectively
Graafian follicle Mature follicle inside the ovary filled with fluid in which the ovum grows
Ovulation The release of an ovum from the Graafian follicle of the ovaries
Endometrium The inner lining of the uterus wall
Menstruation The monthly loss of blood and tissue as a result of changes that occur in the
lining of the uterus
Menopause Stage in the life of a woman when she stops ovulating and menstruating;
usually occurs between the ages of 45 and 55
Fertilisation The fusion of the haploid sperm cell nucleus and the haploid egg cell nucleus to
form a diploid nucleus of the zygote
Implantation The attachment of the embryo to the endometrium lining the uterus
, Human Life cycle:
● All the Somatic cells humans are diploid (2n)
● For humans to grow or to repair damaged tissues, the somatic
cells divide by mitosis.
● The new cells produced by mitosis are identical to the original
cells which were divided.
● Sexual reproduction requires a male & a female.
● They produce gametes (egg/sperm) by meiosis.
● Meiosis ensures that the gametes are haploid (n)
● When 2 gametes fuse as a result of fertilization, a diploid zygote
is formed.
● The zygote then divides by mitosis to form a human.
Male Reproductive System:
Seminiferous tubules in the testes:
● Tubules are lined by germinal epithelium cells which produce sperm
cells.
● Some of the cells develop into Sertoli cells which provide nutrients
for the spermatids to become mature sperm cells.
● Tubules are surrounded by connective tissue that contain Cells of
Leydig which produce testosterone.
● Functions of testosterone:
○ Development of the male secondary sexual characteristics
○ Stimulating the maturation of sperm cells
Reproduction in Vertebrates - 5%
● Diversity of reproductive strategies
Human Reproduction - 27%
● Introduction
● Structure of the male reproductive system
● Structure of the female reproductive system
● Puberty
● Gametogenesis
● Menstrual cycle
● Fertilisation and development of zygote to blastocyst
● Implantation, gestation and the role of the placenta
Responding to the environment (humans) - 36%
● Introduction
● Human nervous system
● Central nervous system
● Peripheral nervous system
● Autonomic nervous system
● Structure and functioning of a nerve
● The simple reflex arc
● Disorders of the CNS
● Receptors
● Human eye
● Human ear
Responding to the Environment (plants) - 9%
● Plant Hormones
● Plant defence mechanisms
Endocrine and Homeostasis (humans) - 23%
● Endocrine system
● Introduction - homeostasis
● Homeostasis: Negative feedback mechanisms
1
,Reproduction in Vertebrates
Key Terminology:
Reproductive strategy Structural, functional and behavioural adaptations that improve
the chances of fertilisation and the survival of offspring
External fertilisation Fertilisation that takes place outside the female’s body, usually in water
Internal fertilisation Fertilisation that occurs inside the female’s body where the male has
deposited its sperm
Ovipary Eggs are laid; the embryo develops outside the mother’s body
Ovovivipary Young develop from eggs fertilised internally and retained within the
mother's body after fertilisation until they hatch
Vivipary The young develop inside the uterus of mother after eggs are fertilised
internally; young are nourished through the placenta
Amniotic egg The embryo inside the egg is protected by a hard shell; the egg consists
of many extra-embryonic membranes that serve different functions
Extra-embryonic membranes Membranes that surround the developing embryo inside the amniotic egg
or uterus.
Amnion Produces amniotic fluid which cushions embryo and protects it from
mechanical injury, temperature changes, dehydration
Allantois Collects the embryo’s nitrogenous waste and assists in the exchange of
gases
Chorion Allows for gaseous exchange in the amniotic egg and forms the placenta
in mammals
Yolk sac Contains the food reserves for the developing embryo
Precocial development When hatchlings are well developed as they hatch, able to move and feed
themselves, with eyes open – limited parental care
Altricial development When hatchlings are underdeveloped as they hatch, unable to move or
feed or fend for themselves – young require more parental care
Parental care Includes the building of nests, protection, teaching of young and feeding
– the care, or lack thereof, directly influences the survival of the young
,External fertilisation and internal fertilisation
● Fertilisation occurs when a haploid sperm cell and egg cell fuse to form a diploid zygote.
External fertilisation Internal fertilisation
Takes place outside female’s body - Requires water Takes place inside female’s body - No water required
Gametes released into water - Spawning - prevents Sperm cells are released into the female’s body
drying out. Egg attracts sperm Not limited to aquatic environment
Little cooperative behaviour A lot of cooperative behaviour
Low chance of fertilization High chance of fertilization
Many gametes released - increases chance of fusion Fewer gametes released - better chance of survival
Many offspring produced Fewer offspring produced
High mortality rates among young due to lack of Lower mortality rates among young as protection is
protection. Eggs can easily desiccate/be predated on. provided by the mother’s body or a hardened
Offspring is independent calcareous / leathery shell. Offspring is dependent
Fish and amphibia Terrestrial vertebrates - reptiles; birds and mammals
Ovipary, ovovivipary and vivipary
Ovipary Ovovivipary Vivipary
Fertilisation external or internal internal internal
Development External to the body of the Inside the body of the female inside the uterus of the
of embryo female - in egg The egg is laid as soon as the female
embryo is fully developed
Nutrition Yolk is form of nutrition Yolk present in the egg. Young receive nutrition from
Aquatic eggs - Less yolk (less the mother’s body through
energy to produce) Young are independent of the placenta
Terrestrial eggs - More yolk the mother’s body
(More energy to produce)
Type of egg Jelly-like or calcareous Calcareous or leathery None
Examples fish, amphibians, reptiles, birds Sharks, lizards and snakes Humans
Amniotic egg
● Water protects aquatic vertebrates eggs from drying out and assists with fertilisation
● Some terrestrial animals need specialised structures to protect the developing embryo from drying out
● Functions of the amniotic egg:
○ Prevents dehydration of the embryo, Provides nutrients (water & oxygen), Remove Waste products
Structure: Function:
Amnion Surrounds the embryo and protects it against shocks,
injuries, temp changes and dehydration
,Allantois Sac that extends from the embryo’s intestines and
collects waste products and exchanges gases
Chorion Outermost membrane.
Bird/reptiles have porous shells for gaseous exchange.
Mammals forms part of the placenta - supplies foetus
with nutrients and helps with gaseous exchange and
excretion
Yolk sac Energy rich yolk provides food for embryo
Albumen Serves as reserve food
Shell Hard, calcareous, leathery and porous for gaseous
exchange - protects embryo
Precocial and altricial development:
Precocial Altricial
Offspring are fully developed and can move around directly Offspring are not fully developed and cannot
after birth move around immediately after birth
Few offspring are produced as lots of energy is used in More offspring are produced
getting to the advanced stage of development before birth
Offspring is faces challenges of environment Parental care afforded to protect from predators.
Less energy used in care of offspring after birth More energy spent on care of offspring are birth
Large amount of yolk for extended incubation period Eggs are smaller and contain less yolk
Mammals: Long gestation period Mammals: Young born ASAP as mothers are
vulnerable to predation
Covered in hair or feathers No hair or feather covering body
Offspring can protect and feed themselves Offspring cannot protect and feed themselves
Parental Care:
● Behaviour of parents in caring for their offspring = Increases chances of survival of the young.
● Eg: Guarding and incubation of eggs, Keeping the young warm, feeding them and protecting them from
predators
● High parental care = low prenatal energy/few offspring produced
● Low parental care = high prenatal energy/many offspring produced
Fish amphibians Reptiles Birds Mammals
No PC Little/no PC Little/no PC A lot of PC Highest PC
Eggs are abandoned Protect eggs Sun incubate eggs Builds nests/ feed Protect young
,Human Reproduction
Key Terminology:
Gamete An egg or sperm cell with half the number of chromosomes
Gametogenesis The process in which gametes are produced in the testes and ovaries through
meiosis oogenesis the process that occurs when egg cells are made in the
ovary through meiosis
Spermatogenesis The process that takes place when sperm cells are made in the testes through
meiosis
Germinal epithelium Cuboidal epithelium found on the surface of the testes and ovaries which gives
rise to the cells which mature to form sperm cells and egg cells respectively
Graafian follicle Mature follicle inside the ovary filled with fluid in which the ovum grows
Ovulation The release of an ovum from the Graafian follicle of the ovaries
Endometrium The inner lining of the uterus wall
Menstruation The monthly loss of blood and tissue as a result of changes that occur in the
lining of the uterus
Menopause Stage in the life of a woman when she stops ovulating and menstruating;
usually occurs between the ages of 45 and 55
Fertilisation The fusion of the haploid sperm cell nucleus and the haploid egg cell nucleus to
form a diploid nucleus of the zygote
Implantation The attachment of the embryo to the endometrium lining the uterus
, Human Life cycle:
● All the Somatic cells humans are diploid (2n)
● For humans to grow or to repair damaged tissues, the somatic
cells divide by mitosis.
● The new cells produced by mitosis are identical to the original
cells which were divided.
● Sexual reproduction requires a male & a female.
● They produce gametes (egg/sperm) by meiosis.
● Meiosis ensures that the gametes are haploid (n)
● When 2 gametes fuse as a result of fertilization, a diploid zygote
is formed.
● The zygote then divides by mitosis to form a human.
Male Reproductive System:
Seminiferous tubules in the testes:
● Tubules are lined by germinal epithelium cells which produce sperm
cells.
● Some of the cells develop into Sertoli cells which provide nutrients
for the spermatids to become mature sperm cells.
● Tubules are surrounded by connective tissue that contain Cells of
Leydig which produce testosterone.
● Functions of testosterone:
○ Development of the male secondary sexual characteristics
○ Stimulating the maturation of sperm cells
